Replace boost::python with pybind11 (#1040)

* Replace boost::python with pybind11

* Replace add_python_module with pybind11_add_module

* Fix clang error on type-dependent expression

dlib/external/pybind11/include/pybind11/functional.h

+/*
+    pybind11/functional.h: std::function<> support
+
+    Copyright (c) 2016 Wenzel Jakob <wenzel.jakob@epfl.ch>
+
+    All rights reserved. Use of this source code is governed by a
+    BSD-style license that can be found in the LICENSE file.
+*/
+
+#pragma once
+
+#include "pybind11.h"
+#include <functional>
+
+NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
+NAMESPACE_BEGIN(detail)
+
+template <typename Return, typename... Args>
+struct type_caster<std::function<Return(Args...)>> {
+    using type = std::function<Return(Args...)>;
+    using retval_type = conditional_t<std::is_same<Return, void>::value, void_type, Return>;
+    using function_type = Return (*) (Args...);
+
+public:
+    bool load(handle src, bool convert) {
+        if (src.is_none()) {
+            // Defer accepting None to other overloads (if we aren't in convert mode):
+            if (!convert) return false;
+            return true;
+        }
+
+        if (!isinstance<function>(src))
+            return false;
+
+        auto func = reinterpret_borrow<function>(src);
+
+        /*
+           When passing a C++ function as an argument to another C++
+           function via Python, every function call would normally involve
+           a full C++ -> Python -> C++ roundtrip, which can be prohibitive.
+           Here, we try to at least detect the case where the function is
+           stateless (i.e. function pointer or lambda function without
+           captured variables), in which case the roundtrip can be avoided.
+         */
+        if (auto cfunc = func.cpp_function()) {
+            auto c = reinterpret_borrow<capsule>(PyCFunction_GET_SELF(cfunc.ptr()));
+            auto rec = (function_record *) c;
+
+            if (rec && rec->is_stateless &&
+                    same_type(typeid(function_type), *reinterpret_cast<const std::type_info *>(rec->data[1]))) {
+                struct capture { function_type f; };
+                value = ((capture *) &rec->data)->f;
+                return true;
+            }
+        }
+
+        value = [func](Args... args) -> Return {
+            gil_scoped_acquire acq;
+            object retval(func(std::forward<Args>(args)...));
+            /* Visual studio 2015 parser issue: need parentheses around this expression */
+            return (retval.template cast<Return>());
+        };
+        return true;
+    }
+
+    template <typename Func>
+    static handle cast(Func &&f_, return_value_policy policy, handle /* parent */) {
+        if (!f_)
+            return none().inc_ref();
+
+        auto result = f_.template target<function_type>();
+        if (result)
+            return cpp_function(*result, policy).release();
+        else
+            return cpp_function(std::forward<Func>(f_), policy).release();
+    }
+
+    PYBIND11_TYPE_CASTER(type, _("Callable[[") + concat(make_caster<Args>::name...) + _("], ")
+                               + make_caster<retval_type>::name + _("]"));
+};
+
+NAMESPACE_END(detail)
+NAMESPACE_END(PYBIND11_NAMESPACE)

dlib/external/pybind11/include/pybind11/iostream.h

+/*
+    pybind11/iostream.h -- Tools to assist with redirecting cout and cerr to Python
+
+    Copyright (c) 2017 Henry F. Schreiner
+
+    All rights reserved. Use of this source code is governed by a
+    BSD-style license that can be found in the LICENSE file.
+*/
+
+#pragma once
+
+#include "pybind11.h"
+
+#include <streambuf>
+#include <ostream>
+#include <string>
+#include <memory>
+#include <iostream>
+
+NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
+NAMESPACE_BEGIN(detail)
+
+// Buffer that writes to Python instead of C++
+class pythonbuf : public std::streambuf {
+private:
+    using traits_type = std::streambuf::traits_type;
+
+    char d_buffer[1024];
+    object pywrite;
+    object pyflush;
+
+    int overflow(int c) {
+        if (!traits_type::eq_int_type(c, traits_type::eof())) {
+            *pptr() = traits_type::to_char_type(c);
+            pbump(1);
+        }
+        return sync() ? traits_type::not_eof(c) : traits_type::eof();
+    }
+
+    int sync() {
+        if (pbase() != pptr()) {
+            // This subtraction cannot be negative, so dropping the sign
+            str line(pbase(), static_cast<size_t>(pptr() - pbase()));
+
+            pywrite(line);
+            pyflush();
+
+            setp(pbase(), epptr());
+        }
+        return 0;
+    }
+
+public:
+    pythonbuf(object pyostream)
+        : pywrite(pyostream.attr("write")),
+          pyflush(pyostream.attr("flush")) {
+        setp(d_buffer, d_buffer + sizeof(d_buffer) - 1);
+    }
+
+    /// Sync before destroy
+    ~pythonbuf() {
+        sync();
+    }
+};
+
+NAMESPACE_END(detail)
+
+
+/** \rst
+    This a move-only guard that redirects output.
+
+    .. code-block:: cpp
+
+        #include <pybind11/iostream.h>
+
+        ...
+
+        {
+            py::scoped_ostream_redirect output;
+            std::cout << "Hello, World!"; // Python stdout
+        } // <-- return std::cout to normal
+
+    You can explicitly pass the c++ stream and the python object,
+    for example to guard stderr instead.
+
+    .. code-block:: cpp
+
+        {
+            py::scoped_ostream_redirect output{std::cerr, py::module::import("sys").attr("stderr")};
+            std::cerr << "Hello, World!";
+        }
+ \endrst */
+class scoped_ostream_redirect {
+protected:
+    std::streambuf *old;
+    std::ostream &costream;
+    detail::pythonbuf buffer;
+
+public:
+    scoped_ostream_redirect(
+            std::ostream &costream = std::cout,
+            object pyostream = module::import("sys").attr("stdout"))
+        : costream(costream), buffer(pyostream) {
+        old = costream.rdbuf(&buffer);
+    }
+
+    ~scoped_ostream_redirect() {
+        costream.rdbuf(old);
+    }
+
+    scoped_ostream_redirect(const scoped_ostream_redirect &) = delete;
+    scoped_ostream_redirect(scoped_ostream_redirect &&other) = default;
+    scoped_ostream_redirect &operator=(const scoped_ostream_redirect &) = delete;
+    scoped_ostream_redirect &operator=(scoped_ostream_redirect &&) = delete;
+};
+
+
+/** \rst
+    Like `scoped_ostream_redirect`, but redirects cerr by default. This class
+    is provided primary to make ``py::call_guard`` easier to make.
+
+    .. code-block:: cpp
+
+     m.def("noisy_func", &noisy_func,
+           py::call_guard<scoped_ostream_redirect,
+                          scoped_estream_redirect>());
+
+\endrst */
+class scoped_estream_redirect : public scoped_ostream_redirect {
+public:
+    scoped_estream_redirect(
+            std::ostream &costream = std::cerr,
+            object pyostream = module::import("sys").attr("stderr"))
+        : scoped_ostream_redirect(costream,pyostream) {}
+};
+
+
+NAMESPACE_BEGIN(detail)
+
+// Class to redirect output as a context manager. C++ backend.
+class OstreamRedirect {
+    bool do_stdout_;
+    bool do_stderr_;
+    std::unique_ptr<scoped_ostream_redirect> redirect_stdout;
+    std::unique_ptr<scoped_estream_redirect> redirect_stderr;
+
+public:
+    OstreamRedirect(bool do_stdout = true, bool do_stderr = true)
+        : do_stdout_(do_stdout), do_stderr_(do_stderr) {}
+
+    void enter() {
+        if (do_stdout_)
+            redirect_stdout.reset(new scoped_ostream_redirect());
+        if (do_stderr_)
+            redirect_stderr.reset(new scoped_estream_redirect());
+    }
+
+    void exit() {
+        redirect_stdout.reset();
+        redirect_stderr.reset();
+    }
+};
+
+NAMESPACE_END(detail)
+
+/** \rst
+    This is a helper function to add a C++ redirect context manager to Python
+    instead of using a C++ guard. To use it, add the following to your binding code:
+
+    .. code-block:: cpp
+
+        #include <pybind11/iostream.h>
+
+        ...
+
+        py::add_ostream_redirect(m, "ostream_redirect");
+
+    You now have a Python context manager that redirects your output:
+
+    .. code-block:: python
+
+        with m.ostream_redirect():
+            m.print_to_cout_function()
+
+    This manager can optionally be told which streams to operate on:
+
+    .. code-block:: python
+
+        with m.ostream_redirect(stdout=true, stderr=true):
+            m.noisy_function_with_error_printing()
+
+ \endrst */
+inline class_<detail::OstreamRedirect> add_ostream_redirect(module m, std::string name = "ostream_redirect") {
+    return class_<detail::OstreamRedirect>(m, name.c_str(), module_local())
+        .def(init<bool,bool>(), arg("stdout")=true, arg("stderr")=true)
+        .def("__enter__", &detail::OstreamRedirect::enter)
+        .def("__exit__", [](detail::OstreamRedirect &self, args) { self.exit(); });
+}
+
+NAMESPACE_END(PYBIND11_NAMESPACE)

dlib/external/pybind11/include/pybind11/numpy.h

+/*
+    pybind11/numpy.h: Basic NumPy support, vectorize() wrapper
+
+    Copyright (c) 2016 Wenzel Jakob <wenzel.jakob@epfl.ch>
+
+    All rights reserved. Use of this source code is governed by a
+    BSD-style license that can be found in the LICENSE file.
+*/
+
+#pragma once
+
+#include "pybind11.h"
+#include "complex.h"
+#include <numeric>
+#include <algorithm>
+#include <array>
+#include <cstdlib>
+#include <cstring>
+#include <sstream>
+#include <string>
+#include <initializer_list>
+#include <functional>
+#include <utility>
+#include <typeindex>
+
+#if defined(_MSC_VER)
+#  pragma warning(push)
+#  pragma warning(disable: 4127) // warning C4127: Conditional expression is constant
+#endif
+
+/* This will be true on all flat address space platforms and allows us to reduce the
+   whole npy_intp / ssize_t / Py_intptr_t business down to just ssize_t for all size
+   and dimension types (e.g. shape, strides, indexing), instead of inflicting this
+   upon the library user. */
+static_assert(sizeof(ssize_t) == sizeof(Py_intptr_t), "ssize_t != Py_intptr_t");
+
+NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
+
+class array; // Forward declaration
+
+NAMESPACE_BEGIN(detail)
+template <typename type, typename SFINAE = void> struct npy_format_descriptor;
+
+struct PyArrayDescr_Proxy {
+    PyObject_HEAD
+    PyObject *typeobj;
+    char kind;
+    char type;
+    char byteorder;
+    char flags;
+    int type_num;
+    int elsize;
+    int alignment;
+    char *subarray;
+    PyObject *fields;
+    PyObject *names;
+};
+
+struct PyArray_Proxy {
+    PyObject_HEAD
+    char *data;
+    int nd;
+    ssize_t *dimensions;
+    ssize_t *strides;
+    PyObject *base;
+    PyObject *descr;
+    int flags;
+};
+
+struct PyVoidScalarObject_Proxy {
+    PyObject_VAR_HEAD
+    char *obval;
+    PyArrayDescr_Proxy *descr;
+    int flags;
+    PyObject *base;
+};
+
+struct numpy_type_info {
+    PyObject* dtype_ptr;
+    std::string format_str;
+};
+
+struct numpy_internals {
+    std::unordered_map<std::type_index, numpy_type_info> registered_dtypes;
+
+    numpy_type_info *get_type_info(const std::type_info& tinfo, bool throw_if_missing = true) {
+        auto it = registered_dtypes.find(std::type_index(tinfo));
+        if (it != registered_dtypes.end())
+            return &(it->second);
+        if (throw_if_missing)
+            pybind11_fail(std::string("NumPy type info missing for ") + tinfo.name());
+        return nullptr;
+    }
+
+    template<typename T> numpy_type_info *get_type_info(bool throw_if_missing = true) {
+        return get_type_info(typeid(typename std::remove_cv<T>::type), throw_if_missing);
+    }
+};
+
+inline PYBIND11_NOINLINE void load_numpy_internals(numpy_internals* &ptr) {
+    ptr = &get_or_create_shared_data<numpy_internals>("_numpy_internals");
+}
+
+inline numpy_internals& get_numpy_internals() {
+    static numpy_internals* ptr = nullptr;
+    if (!ptr)
+        load_numpy_internals(ptr);
+    return *ptr;
+}
+
+struct npy_api {
+    enum constants {
+        NPY_ARRAY_C_CONTIGUOUS_ = 0x0001,
+        NPY_ARRAY_F_CONTIGUOUS_ = 0x0002,
+        NPY_ARRAY_OWNDATA_ = 0x0004,
+        NPY_ARRAY_FORCECAST_ = 0x0010,
+        NPY_ARRAY_ENSUREARRAY_ = 0x0040,
+        NPY_ARRAY_ALIGNED_ = 0x0100,
+        NPY_ARRAY_WRITEABLE_ = 0x0400,
+        NPY_BOOL_ = 0,
+        NPY_BYTE_, NPY_UBYTE_,
+        NPY_SHORT_, NPY_USHORT_,
+        NPY_INT_, NPY_UINT_,
+        NPY_LONG_, NPY_ULONG_,
+        NPY_LONGLONG_, NPY_ULONGLONG_,
+        NPY_FLOAT_, NPY_DOUBLE_, NPY_LONGDOUBLE_,
+        NPY_CFLOAT_, NPY_CDOUBLE_, NPY_CLONGDOUBLE_,
+        NPY_OBJECT_ = 17,
+        NPY_STRING_, NPY_UNICODE_, NPY_VOID_
+    };
+
+    typedef struct {
+        Py_intptr_t *ptr;
+        int len;
+    } PyArray_Dims;
+
+    static npy_api& get() {
+        static npy_api api = lookup();
+        return api;
+    }
+
+    bool PyArray_Check_(PyObject *obj) const {
+        return (bool) PyObject_TypeCheck(obj, PyArray_Type_);
+    }
+    bool PyArrayDescr_Check_(PyObject *obj) const {
+        return (bool) PyObject_TypeCheck(obj, PyArrayDescr_Type_);
+    }
+
+    unsigned int (*PyArray_GetNDArrayCFeatureVersion_)();
+    PyObject *(*PyArray_DescrFromType_)(int);
+    PyObject *(*PyArray_NewFromDescr_)
+        (PyTypeObject *, PyObject *, int, Py_intptr_t *,
+         Py_intptr_t *, void *, int, PyObject *);
+    PyObject *(*PyArray_DescrNewFromType_)(int);
+    int (*PyArray_CopyInto_)(PyObject *, PyObject *);
+    PyObject *(*PyArray_NewCopy_)(PyObject *, int);
+    PyTypeObject *PyArray_Type_;
+    PyTypeObject *PyVoidArrType_Type_;
+    PyTypeObject *PyArrayDescr_Type_;
+    PyObject *(*PyArray_DescrFromScalar_)(PyObject *);
+    PyObject *(*PyArray_FromAny_) (PyObject *, PyObject *, int, int, int, PyObject *);
+    int (*PyArray_DescrConverter_) (PyObject *, PyObject **);
+    bool (*PyArray_EquivTypes_) (PyObject *, PyObject *);
+    int (*PyArray_GetArrayParamsFromObject_)(PyObject *, PyObject *, char, PyObject **, int *,
+                                             Py_ssize_t *, PyObject **, PyObject *);
+    PyObject *(*PyArray_Squeeze_)(PyObject *);
+    int (*PyArray_SetBaseObject_)(PyObject *, PyObject *);
+    PyObject* (*PyArray_Resize_)(PyObject*, PyArray_Dims*, int, int);
+private:
+    enum functions {
+        API_PyArray_GetNDArrayCFeatureVersion = 211,
+        API_PyArray_Type = 2,
+        API_PyArrayDescr_Type = 3,
+        API_PyVoidArrType_Type = 39,
+        API_PyArray_DescrFromType = 45,
+        API_PyArray_DescrFromScalar = 57,
+        API_PyArray_FromAny = 69,
+        API_PyArray_Resize = 80,
+        API_PyArray_CopyInto = 82,
+        API_PyArray_NewCopy = 85,
+        API_PyArray_NewFromDescr = 94,
+        API_PyArray_DescrNewFromType = 9,
+        API_PyArray_DescrConverter = 174,
+        API_PyArray_EquivTypes = 182,
+        API_PyArray_GetArrayParamsFromObject = 278,
+        API_PyArray_Squeeze = 136,
+        API_PyArray_SetBaseObject = 282
+    };
+
+    static npy_api lookup() {
+        module m = module::import("numpy.core.multiarray");
+        auto c = m.attr("_ARRAY_API");
+#if PY_MAJOR_VERSION >= 3
+        void **api_ptr = (void **) PyCapsule_GetPointer(c.ptr(), NULL);
+#else
+        void **api_ptr = (void **) PyCObject_AsVoidPtr(c.ptr());
+#endif
+        npy_api api;
+#define DECL_NPY_API(Func) api.Func##_ = (decltype(api.Func##_)) api_ptr[API_##Func];
+        DECL_NPY_API(PyArray_GetNDArrayCFeatureVersion);
+        if (api.PyArray_GetNDArrayCFeatureVersion_() < 0x7)
+            pybind11_fail("pybind11 numpy support requires numpy >= 1.7.0");
+        DECL_NPY_API(PyArray_Type);
+        DECL_NPY_API(PyVoidArrType_Type);
+        DECL_NPY_API(PyArrayDescr_Type);
+        DECL_NPY_API(PyArray_DescrFromType);
+        DECL_NPY_API(PyArray_DescrFromScalar);
+        DECL_NPY_API(PyArray_FromAny);
+        DECL_NPY_API(PyArray_Resize);
+        DECL_NPY_API(PyArray_CopyInto);
+        DECL_NPY_API(PyArray_NewCopy);
+        DECL_NPY_API(PyArray_NewFromDescr);
+        DECL_NPY_API(PyArray_DescrNewFromType);
+        DECL_NPY_API(PyArray_DescrConverter);
+        DECL_NPY_API(PyArray_EquivTypes);
+        DECL_NPY_API(PyArray_GetArrayParamsFromObject);
+        DECL_NPY_API(PyArray_Squeeze);
+        DECL_NPY_API(PyArray_SetBaseObject);
+#undef DECL_NPY_API
+        return api;
+    }
+};
+
+inline PyArray_Proxy* array_proxy(void* ptr) {
+    return reinterpret_cast<PyArray_Proxy*>(ptr);
+}
+
+inline const PyArray_Proxy* array_proxy(const void* ptr) {
+    return reinterpret_cast<const PyArray_Proxy*>(ptr);
+}
+
+inline PyArrayDescr_Proxy* array_descriptor_proxy(PyObject* ptr) {
+   return reinterpret_cast<PyArrayDescr_Proxy*>(ptr);
+}
+
+inline const PyArrayDescr_Proxy* array_descriptor_proxy(const PyObject* ptr) {
+   return reinterpret_cast<const PyArrayDescr_Proxy*>(ptr);
+}
+
+inline bool check_flags(const void* ptr, int flag) {
+    return (flag == (array_proxy(ptr)->flags & flag));
+}
+
+template <typename T> struct is_std_array : std::false_type { };
+template <typename T, size_t N> struct is_std_array<std::array<T, N>> : std::true_type { };
+template <typename T> struct is_complex : std::false_type { };
+template <typename T> struct is_complex<std::complex<T>> : std::true_type { };
+
+template <typename T> struct array_info_scalar {
+    typedef T type;
+    static constexpr bool is_array = false;
+    static constexpr bool is_empty = false;
+    static constexpr auto extents = _("");
+    static void append_extents(list& /* shape */) { }
+};
+// Computes underlying type and a comma-separated list of extents for array
+// types (any mix of std::array and built-in arrays). An array of char is
+// treated as scalar because it gets special handling.
+template <typename T> struct array_info : array_info_scalar<T> { };
+template <typename T, size_t N> struct array_info<std::array<T, N>> {
+    using type = typename array_info<T>::type;
+    static constexpr bool is_array = true;
+    static constexpr bool is_empty = (N == 0) || array_info<T>::is_empty;
+    static constexpr size_t extent = N;
+
+    // appends the extents to shape
+    static void append_extents(list& shape) {
+        shape.append(N);
+        array_info<T>::append_extents(shape);
+    }
+
+    static constexpr auto extents = _<array_info<T>::is_array>(
+        concat(_<N>(), array_info<T>::extents), _<N>()
+    );
+};
+// For numpy we have special handling for arrays of characters, so we don't include
+// the size in the array extents.
+template <size_t N> struct array_info<char[N]> : array_info_scalar<char[N]> { };
+template <size_t N> struct array_info<std::array<char, N>> : array_info_scalar<std::array<char, N>> { };
+template <typename T, size_t N> struct array_info<T[N]> : array_info<std::array<T, N>> { };
+template <typename T> using remove_all_extents_t = typename array_info<T>::type;
+
+template <typename T> using is_pod_struct = all_of<
+    std::is_standard_layout<T>,     // since we're accessing directly in memory we need a standard layout type
+#if !defined(__GNUG__) || defined(_LIBCPP_VERSION) || defined(_GLIBCXX_USE_CXX11_ABI)
+    // _GLIBCXX_USE_CXX11_ABI indicates that we're using libstdc++ from GCC 5 or newer, independent
+    // of the actual compiler (Clang can also use libstdc++, but it always defines __GNUC__ == 4).
+    std::is_trivially_copyable<T>,
+#else
+    // GCC 4 doesn't implement is_trivially_copyable, so approximate it
+    std::is_trivially_destructible<T>,
+    satisfies_any_of<T, std::has_trivial_copy_constructor, std::has_trivial_copy_assign>,
+#endif
+    satisfies_none_of<T, std::is_reference, std::is_array, is_std_array, std::is_arithmetic, is_complex, std::is_enum>
+>;
+
+template <ssize_t Dim = 0, typename Strides> ssize_t byte_offset_unsafe(const Strides &) { return 0; }
+template <ssize_t Dim = 0, typename Strides, typename... Ix>
+ssize_t byte_offset_unsafe(const Strides &strides, ssize_t i, Ix... index) {
+    return i * strides[Dim] + byte_offset_unsafe<Dim + 1>(strides, index...);
+}
+
+/**
+ * Proxy class providing unsafe, unchecked const access to array data.  This is constructed through
+ * the `unchecked<T, N>()` method of `array` or the `unchecked<N>()` method of `array_t<T>`.  `Dims`
+ * will be -1 for dimensions determined at runtime.
+ */
+template <typename T, ssize_t Dims>
+class unchecked_reference {
+protected:
+    static constexpr bool Dynamic = Dims < 0;
+    const unsigned char *data_;
+    // Storing the shape & strides in local variables (i.e. these arrays) allows the compiler to
+    // make large performance gains on big, nested loops, but requires compile-time dimensions
+    conditional_t<Dynamic, const ssize_t *, std::array<ssize_t, (size_t) Dims>>
+            shape_, strides_;
+    const ssize_t dims_;
+
+    friend class pybind11::array;
+    // Constructor for compile-time dimensions:
+    template <bool Dyn = Dynamic>
+    unchecked_reference(const void *data, const ssize_t *shape, const ssize_t *strides, enable_if_t<!Dyn, ssize_t>)
+    : data_{reinterpret_cast<const unsigned char *>(data)}, dims_{Dims} {
+        for (size_t i = 0; i < (size_t) dims_; i++) {
+            shape_[i] = shape[i];
+            strides_[i] = strides[i];
+        }
+    }
+    // Constructor for runtime dimensions:
+    template <bool Dyn = Dynamic>
+    unchecked_reference(const void *data, const ssize_t *shape, const ssize_t *strides, enable_if_t<Dyn, ssize_t> dims)
+    : data_{reinterpret_cast<const unsigned char *>(data)}, shape_{shape}, strides_{strides}, dims_{dims} {}
+
+public:
+    /**
+     * Unchecked const reference access to data at the given indices.  For a compile-time known
+     * number of dimensions, this requires the correct number of arguments; for run-time
+     * dimensionality, this is not checked (and so is up to the caller to use safely).
+     */
+    template <typename... Ix> const T &operator()(Ix... index) const {
+        static_assert(ssize_t{sizeof...(Ix)} == Dims || Dynamic,
+                "Invalid number of indices for unchecked array reference");
+        return *reinterpret_cast<const T *>(data_ + byte_offset_unsafe(strides_, ssize_t(index)...));
+    }
+    /**
+     * Unchecked const reference access to data; this operator only participates if the reference
+     * is to a 1-dimensional array.  When present, this is exactly equivalent to `obj(index)`.
+     */
+    template <ssize_t D = Dims, typename = enable_if_t<D == 1 || Dynamic>>
+    const T &operator[](ssize_t index) const { return operator()(index); }
+
+    /// Pointer access to the data at the given indices.
+    template <typename... Ix> const T *data(Ix... ix) const { return &operator()(ssize_t(ix)...); }
+
+    /// Returns the item size, i.e. sizeof(T)
+    constexpr static ssize_t itemsize() { return sizeof(T); }
+
+    /// Returns the shape (i.e. size) of dimension `dim`
+    ssize_t shape(ssize_t dim) const { return shape_[(size_t) dim]; }
+
+    /// Returns the number of dimensions of the array
+    ssize_t ndim() const { return dims_; }
+
+    /// Returns the total number of elements in the referenced array, i.e. the product of the shapes
+    template <bool Dyn = Dynamic>
+    enable_if_t<!Dyn, ssize_t> size() const {
+        return std::accumulate(shape_.begin(), shape_.end(), (ssize_t) 1, std::multiplies<ssize_t>());
+    }
+    template <bool Dyn = Dynamic>
+    enable_if_t<Dyn, ssize_t> size() const {
+        return std::accumulate(shape_, shape_ + ndim(), (ssize_t) 1, std::multiplies<ssize_t>());
+    }
+
+    /// Returns the total number of bytes used by the referenced data.  Note that the actual span in
+    /// memory may be larger if the referenced array has non-contiguous strides (e.g. for a slice).
+    ssize_t nbytes() const {
+        return size() * itemsize();
+    }
+};
+
+template <typename T, ssize_t Dims>
+class unchecked_mutable_reference : public unchecked_reference<T, Dims> {
+    friend class pybind11::array;
+    using ConstBase = unchecked_reference<T, Dims>;
+    using ConstBase::ConstBase;
+    using ConstBase::Dynamic;
+public:
+    /// Mutable, unchecked access to data at the given indices.
+    template <typename... Ix> T& operator()(Ix... index) {
+        static_assert(ssize_t{sizeof...(Ix)} == Dims || Dynamic,
+                "Invalid number of indices for unchecked array reference");
+        return const_cast<T &>(ConstBase::operator()(index...));
+    }
+    /**
+     * Mutable, unchecked access data at the given index; this operator only participates if the
+     * reference is to a 1-dimensional array (or has runtime dimensions).  When present, this is
+     * exactly equivalent to `obj(index)`.
+     */
+    template <ssize_t D = Dims, typename = enable_if_t<D == 1 || Dynamic>>
+    T &operator[](ssize_t index) { return operator()(index); }
+
+    /// Mutable pointer access to the data at the given indices.
+    template <typename... Ix> T *mutable_data(Ix... ix) { return &operator()(ssize_t(ix)...); }
+};
+
+template <typename T, ssize_t Dim>
+struct type_caster<unchecked_reference<T, Dim>> {
+    static_assert(Dim == 0 && Dim > 0 /* always fail */, "unchecked array proxy object is not castable");
+};
+template <typename T, ssize_t Dim>
+struct type_caster<unchecked_mutable_reference<T, Dim>> : type_caster<unchecked_reference<T, Dim>> {};
+
+NAMESPACE_END(detail)
+
+class dtype : public object {
+public:
+    PYBIND11_OBJECT_DEFAULT(dtype, object, detail::npy_api::get().PyArrayDescr_Check_);
+
+    explicit dtype(const buffer_info &info) {
+        dtype descr(_dtype_from_pep3118()(PYBIND11_STR_TYPE(info.format)));
+        // If info.itemsize == 0, use the value calculated from the format string
+        m_ptr = descr.strip_padding(info.itemsize ? info.itemsize : descr.itemsize()).release().ptr();
+    }
+
+    explicit dtype(const std::string &format) {
+        m_ptr = from_args(pybind11::str(format)).release().ptr();
+    }
+
+    dtype(const char *format) : dtype(std::string(format)) { }
+
+    dtype(list names, list formats, list offsets, ssize_t itemsize) {
+        dict args;
+        args["names"] = names;
+        args["formats"] = formats;
+        args["offsets"] = offsets;
+        args["itemsize"] = pybind11::int_(itemsize);
+        m_ptr = from_args(args).release().ptr();
+    }
+
+    /// This is essentially the same as calling numpy.dtype(args) in Python.
+    static dtype from_args(object args) {
+        PyObject *ptr = nullptr;
+        if (!detail::npy_api::get().PyArray_DescrConverter_(args.ptr(), &ptr) || !ptr)
+            throw error_already_set();
+        return reinterpret_steal<dtype>(ptr);
+    }
+
+    /// Return dtype associated with a C++ type.
+    template <typename T> static dtype of() {
+        return detail::npy_format_descriptor<typename std::remove_cv<T>::type>::dtype();
+    }
+
+    /// Size of the data type in bytes.
+    ssize_t itemsize() const {
+        return detail::array_descriptor_proxy(m_ptr)->elsize;
+    }
+
+    /// Returns true for structured data types.
+    bool has_fields() const {
+        return detail::array_descriptor_proxy(m_ptr)->names != nullptr;
+    }
+
+    /// Single-character type code.
+    char kind() const {
+        return detail::array_descriptor_proxy(m_ptr)->kind;
+    }
+
+private:
+    static object _dtype_from_pep3118() {
+        static PyObject *obj = module::import("numpy.core._internal")
+            .attr("_dtype_from_pep3118").cast<object>().release().ptr();
+        return reinterpret_borrow<object>(obj);
+    }
+
+    dtype strip_padding(ssize_t itemsize) {
+        // Recursively strip all void fields with empty names that are generated for
+        // padding fields (as of NumPy v1.11).
+        if (!has_fields())
+            return *this;
+
+        struct field_descr { PYBIND11_STR_TYPE name; object format; pybind11::int_ offset; };
+        std::vector<field_descr> field_descriptors;
+
+        for (auto field : attr("fields").attr("items")()) {
+            auto spec = field.cast<tuple>();
+            auto name = spec[0].cast<pybind11::str>();
+            auto format = spec[1].cast<tuple>()[0].cast<dtype>();
+            auto offset = spec[1].cast<tuple>()[1].cast<pybind11::int_>();
+            if (!len(name) && format.kind() == 'V')
+                continue;
+            field_descriptors.push_back({(PYBIND11_STR_TYPE) name, format.strip_padding(format.itemsize()), offset});
+        }
+
+        std::sort(field_descriptors.begin(), field_descriptors.end(),
+                  [](const field_descr& a, const field_descr& b) {
+                      return a.offset.cast<int>() < b.offset.cast<int>();
+                  });
+
+        list names, formats, offsets;
+        for (auto& descr : field_descriptors) {
+            names.append(descr.name);
+            formats.append(descr.format);
+            offsets.append(descr.offset);
+        }
+        return dtype(names, formats, offsets, itemsize);
+    }
+};
+
+class array : public buffer {
+public:
+    PYBIND11_OBJECT_CVT(array, buffer, detail::npy_api::get().PyArray_Check_, raw_array)
+
+    enum {
+        c_style = detail::npy_api::NPY_ARRAY_C_CONTIGUOUS_,
+        f_style = detail::npy_api::NPY_ARRAY_F_CONTIGUOUS_,
+        forcecast = detail::npy_api::NPY_ARRAY_FORCECAST_
+    };
+
+    array() : array({{0}}, static_cast<const double *>(nullptr)) {}
+
+    using ShapeContainer = detail::any_container<ssize_t>;
+    using StridesContainer = detail::any_container<ssize_t>;
+
+    // Constructs an array taking shape/strides from arbitrary container types
+    array(const pybind11::dtype &dt, ShapeContainer shape, StridesContainer strides,
+          const void *ptr = nullptr, handle base = handle()) {
+
+        if (strides->empty())
+            *strides = c_strides(*shape, dt.itemsize());
+
+        auto ndim = shape->size();
+        if (ndim != strides->size())
+            pybind11_fail("NumPy: shape ndim doesn't match strides ndim");
+        auto descr = dt;
+
+        int flags = 0;
+        if (base && ptr) {
+            if (isinstance<array>(base))
+                /* Copy flags from base (except ownership bit) */
+                flags = reinterpret_borrow<array>(base).flags() & ~detail::npy_api::NPY_ARRAY_OWNDATA_;
+            else
+                /* Writable by default, easy to downgrade later on if needed */
+                flags = detail::npy_api::NPY_ARRAY_WRITEABLE_;
+        }
+
+        auto &api = detail::npy_api::get();
+        auto tmp = reinterpret_steal<object>(api.PyArray_NewFromDescr_(
+            api.PyArray_Type_, descr.release().ptr(), (int) ndim, shape->data(), strides->data(),
+            const_cast<void *>(ptr), flags, nullptr));
+        if (!tmp)
+            throw error_already_set();
+        if (ptr) {
+            if (base) {
+                api.PyArray_SetBaseObject_(tmp.ptr(), base.inc_ref().ptr());
+            } else {
+                tmp = reinterpret_steal<object>(api.PyArray_NewCopy_(tmp.ptr(), -1 /* any order */));
+            }
+        }
+        m_ptr = tmp.release().ptr();
+    }
+
+    array(const pybind11::dtype &dt, ShapeContainer shape, const void *ptr = nullptr, handle base = handle())
+        : array(dt, std::move(shape), {}, ptr, base) { }
+
+    template <typename T, typename = detail::enable_if_t<std::is_integral<T>::value && !std::is_same<bool, T>::value>>
+    array(const pybind11::dtype &dt, T count, const void *ptr = nullptr, handle base = handle())
+        : array(dt, {{count}}, ptr, base) { }
+
+    template <typename T>
+    array(ShapeContainer shape, StridesContainer strides, const T *ptr, handle base = handle())
+        : array(pybind11::dtype::of<T>(), std::move(shape), std::move(strides), ptr, base) { }
+
+    template <typename T>
+    array(ShapeContainer shape, const T *ptr, handle base = handle())
+        : array(std::move(shape), {}, ptr, base) { }
+
+    template <typename T>
+    explicit array(ssize_t count, const T *ptr, handle base = handle()) : array({count}, {}, ptr, base) { }
+
+    explicit array(const buffer_info &info)
+    : array(pybind11::dtype(info), info.shape, info.strides, info.ptr) { }
+
+    /// Array descriptor (dtype)
+    pybind11::dtype dtype() const {
+        return reinterpret_borrow<pybind11::dtype>(detail::array_proxy(m_ptr)->descr);
+    }
+
+    /// Total number of elements
+    ssize_t size() const {
+        return std::accumulate(shape(), shape() + ndim(), (ssize_t) 1, std::multiplies<ssize_t>());
+    }
+
+    /// Byte size of a single element
+    ssize_t itemsize() const {
+        return detail::array_descriptor_proxy(detail::array_proxy(m_ptr)->descr)->elsize;
+    }
+
+    /// Total number of bytes
+    ssize_t nbytes() const {
+        return size() * itemsize();
+    }
+
+    /// Number of dimensions
+    ssize_t ndim() const {
+        return detail::array_proxy(m_ptr)->nd;
+    }
+
+    /// Base object
+    object base() const {
+        return reinterpret_borrow<object>(detail::array_proxy(m_ptr)->base);
+    }
+
+    /// Dimensions of the array
+    const ssize_t* shape() const {
+        return detail::array_proxy(m_ptr)->dimensions;
+    }
+
+    /// Dimension along a given axis
+    ssize_t shape(ssize_t dim) const {
+        if (dim >= ndim())
+            fail_dim_check(dim, "invalid axis");
+        return shape()[dim];
+    }
+
+    /// Strides of the array
+    const ssize_t* strides() const {
+        return detail::array_proxy(m_ptr)->strides;
+    }
+
+    /// Stride along a given axis
+    ssize_t strides(ssize_t dim) const {
+        if (dim >= ndim())
+            fail_dim_check(dim, "invalid axis");
+        return strides()[dim];
+    }
+
+    /// Return the NumPy array flags
+    int flags() const {
+        return detail::array_proxy(m_ptr)->flags;
+    }
+
+    /// If set, the array is writeable (otherwise the buffer is read-only)
+    bool writeable() const {
+        return detail::check_flags(m_ptr, detail::npy_api::NPY_ARRAY_WRITEABLE_);
+    }
+
+    /// If set, the array owns the data (will be freed when the array is deleted)
+    bool owndata() const {
+        return detail::check_flags(m_ptr, detail::npy_api::NPY_ARRAY_OWNDATA_);
+    }
+
+    /// Pointer to the contained data. If index is not provided, points to the
+    /// beginning of the buffer. May throw if the index would lead to out of bounds access.
+    template<typename... Ix> const void* data(Ix... index) const {
+        return static_cast<const void *>(detail::array_proxy(m_ptr)->data + offset_at(index...));
+    }
+
+    /// Mutable pointer to the contained data. If index is not provided, points to the
+    /// beginning of the buffer. May throw if the index would lead to out of bounds access.
+    /// May throw if the array is not writeable.
+    template<typename... Ix> void* mutable_data(Ix... index) {
+        check_writeable();
+        return static_cast<void *>(detail::array_proxy(m_ptr)->data + offset_at(index...));
+    }
+
+    /// Byte offset from beginning of the array to a given index (full or partial).
+    /// May throw if the index would lead to out of bounds access.
+    template<typename... Ix> ssize_t offset_at(Ix... index) const {
+        if ((ssize_t) sizeof...(index) > ndim())
+            fail_dim_check(sizeof...(index), "too many indices for an array");
+        return byte_offset(ssize_t(index)...);
+    }
+
+    ssize_t offset_at() const { return 0; }
+
+    /// Item count from beginning of the array to a given index (full or partial).
+    /// May throw if the index would lead to out of bounds access.
+    template<typename... Ix> ssize_t index_at(Ix... index) const {
+        return offset_at(index...) / itemsize();
+    }
+
+    /**
+     * Returns a proxy object that provides access to the array's data without bounds or
+     * dimensionality checking.  Will throw if the array is missing the `writeable` flag.  Use with
+     * care: the array must not be destroyed or reshaped for the duration of the returned object,
+     * and the caller must take care not to access invalid dimensions or dimension indices.
+     */
+    template <typename T, ssize_t Dims = -1> detail::unchecked_mutable_reference<T, Dims> mutable_unchecked() & {
+        if (Dims >= 0 && ndim() != Dims)
+            throw std::domain_error("array has incorrect number of dimensions: " + std::to_string(ndim()) +
+                    "; expected " + std::to_string(Dims));
+        return detail::unchecked_mutable_reference<T, Dims>(mutable_data(), shape(), strides(), ndim());
+    }
+
+    /**
+     * Returns a proxy object that provides const access to the array's data without bounds or
+     * dimensionality checking.  Unlike `mutable_unchecked()`, this does not require that the
+     * underlying array have the `writable` flag.  Use with care: the array must not be destroyed or
+     * reshaped for the duration of the returned object, and the caller must take care not to access
+     * invalid dimensions or dimension indices.
+     */
+    template <typename T, ssize_t Dims = -1> detail::unchecked_reference<T, Dims> unchecked() const & {
+        if (Dims >= 0 && ndim() != Dims)
+            throw std::domain_error("array has incorrect number of dimensions: " + std::to_string(ndim()) +
+                    "; expected " + std::to_string(Dims));
+        return detail::unchecked_reference<T, Dims>(data(), shape(), strides(), ndim());
+    }
+
+    /// Return a new view with all of the dimensions of length 1 removed
+    array squeeze() {
+        auto& api = detail::npy_api::get();
+        return reinterpret_steal<array>(api.PyArray_Squeeze_(m_ptr));
+    }
+
+    /// Resize array to given shape
+    /// If refcheck is true and more that one reference exist to this array
+    /// then resize will succeed only if it makes a reshape, i.e. original size doesn't change
+    void resize(ShapeContainer new_shape, bool refcheck = true) {
+        detail::npy_api::PyArray_Dims d = {
+            new_shape->data(), int(new_shape->size())
+        };
+        // try to resize, set ordering param to -1 cause it's not used anyway
+        object new_array = reinterpret_steal<object>(
+            detail::npy_api::get().PyArray_Resize_(m_ptr, &d, int(refcheck), -1)
+        );
+        if (!new_array) throw error_already_set();
+        if (isinstance<array>(new_array)) { *this = std::move(new_array); }
+    }
+
+    /// Ensure that the argument is a NumPy array
+    /// In case of an error, nullptr is returned and the Python error is cleared.
+    static array ensure(handle h, int ExtraFlags = 0) {
+        auto result = reinterpret_steal<array>(raw_array(h.ptr(), ExtraFlags));
+        if (!result)
+            PyErr_Clear();
+        return result;
+    }
+
+protected:
+    template<typename, typename> friend struct detail::npy_format_descriptor;
+
+    void fail_dim_check(ssize_t dim, const std::string& msg) const {
+        throw index_error(msg + ": " + std::to_string(dim) +
+                          " (ndim = " + std::to_string(ndim()) + ")");
+    }
+
+    template<typename... Ix> ssize_t byte_offset(Ix... index) const {
+        check_dimensions(index...);
+        return detail::byte_offset_unsafe(strides(), ssize_t(index)...);
+    }
+
+    void check_writeable() const {
+        if (!writeable())
+            throw std::domain_error("array is not writeable");
+    }
+
+    // Default, C-style strides
+    static std::vector<ssize_t> c_strides(const std::vector<ssize_t> &shape, ssize_t itemsize) {
+        auto ndim = shape.size();
+        std::vector<ssize_t> strides(ndim, itemsize);
+        for (size_t i = ndim - 1; i > 0; --i)
+            strides[i - 1] = strides[i] * shape[i];
+        return strides;
+    }
+
+    // F-style strides; default when constructing an array_t with `ExtraFlags & f_style`
+    static std::vector<ssize_t> f_strides(const std::vector<ssize_t> &shape, ssize_t itemsize) {
+        auto ndim = shape.size();
+        std::vector<ssize_t> strides(ndim, itemsize);
+        for (size_t i = 1; i < ndim; ++i)
+            strides[i] = strides[i - 1] * shape[i - 1];
+        return strides;
+    }
+
+    template<typename... Ix> void check_dimensions(Ix... index) const {
+        check_dimensions_impl(ssize_t(0), shape(), ssize_t(index)...);
+    }
+
+    void check_dimensions_impl(ssize_t, const ssize_t*) const { }
+
+    template<typename... Ix> void check_dimensions_impl(ssize_t axis, const ssize_t* shape, ssize_t i, Ix... index) const {
+        if (i >= *shape) {
+            throw index_error(std::string("index ") + std::to_string(i) +
+                              " is out of bounds for axis " + std::to_string(axis) +
+                              " with size " + std::to_string(*shape));
+        }
+        check_dimensions_impl(axis + 1, shape + 1, index...);
+    }
+
+    /// Create array from any object -- always returns a new reference
+    static PyObject *raw_array(PyObject *ptr, int ExtraFlags = 0) {
+        if (ptr == nullptr) {
+            PyErr_SetString(PyExc_ValueError, "cannot create a pybind11::array from a nullptr");
+            return nullptr;
+        }
+        return detail::npy_api::get().PyArray_FromAny_(
+            ptr, nullptr, 0, 0, detail::npy_api::NPY_ARRAY_ENSUREARRAY_ | ExtraFlags, nullptr);
+    }
+};
+
+template <typename T, int ExtraFlags = array::forcecast> class array_t : public array {
+private:
+    struct private_ctor {};
+    // Delegating constructor needed when both moving and accessing in the same constructor
+    array_t(private_ctor, ShapeContainer &&shape, StridesContainer &&strides, const T *ptr, handle base)
+        : array(std::move(shape), std::move(strides), ptr, base) {}
+public:
+    static_assert(!detail::array_info<T>::is_array, "Array types cannot be used with array_t");
+
+    using value_type = T;
+
+    array_t() : array(0, static_cast<const T *>(nullptr)) {}
+    array_t(handle h, borrowed_t) : array(h, borrowed_t{}) { }
+    array_t(handle h, stolen_t) : array(h, stolen_t{}) { }
+
+    PYBIND11_DEPRECATED("Use array_t<T>::ensure() instead")
+    array_t(handle h, bool is_borrowed) : array(raw_array_t(h.ptr()), stolen_t{}) {
+        if (!m_ptr) PyErr_Clear();
+        if (!is_borrowed) Py_XDECREF(h.ptr());
+    }
+
+    array_t(const object &o) : array(raw_array_t(o.ptr()), stolen_t{}) {
+        if (!m_ptr) throw error_already_set();
+    }
+
+    explicit array_t(const buffer_info& info) : array(info) { }
+
+    array_t(ShapeContainer shape, StridesContainer strides, const T *ptr = nullptr, handle base = handle())
+        : array(std::move(shape), std::move(strides), ptr, base) { }
+
+    explicit array_t(ShapeContainer shape, const T *ptr = nullptr, handle base = handle())
+        : array_t(private_ctor{}, std::move(shape),
+                ExtraFlags & f_style ? f_strides(*shape, itemsize()) : c_strides(*shape, itemsize()),
+                ptr, base) { }
+
+    explicit array_t(size_t count, const T *ptr = nullptr, handle base = handle())
+        : array({count}, {}, ptr, base) { }
+
+    constexpr ssize_t itemsize() const {
+        return sizeof(T);
+    }
+
+    template<typename... Ix> ssize_t index_at(Ix... index) const {
+        return offset_at(index...) / itemsize();
+    }
+
+    template<typename... Ix> const T* data(Ix... index) const {
+        return static_cast<const T*>(array::data(index...));
+    }
+
+    template<typename... Ix> T* mutable_data(Ix... index) {
+        return static_cast<T*>(array::mutable_data(index...));
+    }
+
+    // Reference to element at a given index
+    template<typename... Ix> const T& at(Ix... index) const {
+        if (sizeof...(index) != ndim())
+            fail_dim_check(sizeof...(index), "index dimension mismatch");
+        return *(static_cast<const T*>(array::data()) + byte_offset(ssize_t(index)...) / itemsize());
+    }
+
+    // Mutable reference to element at a given index
+    template<typename... Ix> T& mutable_at(Ix... index) {
+        if (sizeof...(index) != ndim())
+            fail_dim_check(sizeof...(index), "index dimension mismatch");
+        return *(static_cast<T*>(array::mutable_data()) + byte_offset(ssize_t(index)...) / itemsize());
+    }
+
+    /**
+     * Returns a proxy object that provides access to the array's data without bounds or
+     * dimensionality checking.  Will throw if the array is missing the `writeable` flag.  Use with
+     * care: the array must not be destroyed or reshaped for the duration of the returned object,
+     * and the caller must take care not to access invalid dimensions or dimension indices.
+     */
+    template <ssize_t Dims = -1> detail::unchecked_mutable_reference<T, Dims> mutable_unchecked() & {
+        return array::mutable_unchecked<T, Dims>();
+    }
+
+    /**
+     * Returns a proxy object that provides const access to the array's data without bounds or
+     * dimensionality checking.  Unlike `unchecked()`, this does not require that the underlying
+     * array have the `writable` flag.  Use with care: the array must not be destroyed or reshaped
+     * for the duration of the returned object, and the caller must take care not to access invalid
+     * dimensions or dimension indices.
+     */
+    template <ssize_t Dims = -1> detail::unchecked_reference<T, Dims> unchecked() const & {
+        return array::unchecked<T, Dims>();
+    }
+
+    /// Ensure that the argument is a NumPy array of the correct dtype (and if not, try to convert
+    /// it).  In case of an error, nullptr is returned and the Python error is cleared.
+    static array_t ensure(handle h) {
+        auto result = reinterpret_steal<array_t>(raw_array_t(h.ptr()));
+        if (!result)
+            PyErr_Clear();
+        return result;
+    }
+
+    static bool check_(handle h) {
+        const auto &api = detail::npy_api::get();
+        return api.PyArray_Check_(h.ptr())
+               && api.PyArray_EquivTypes_(detail::array_proxy(h.ptr())->descr, dtype::of<T>().ptr());
+    }
+
+protected:
+    /// Create array from any object -- always returns a new reference
+    static PyObject *raw_array_t(PyObject *ptr) {
+        if (ptr == nullptr) {
+            PyErr_SetString(PyExc_ValueError, "cannot create a pybind11::array_t from a nullptr");
+            return nullptr;
+        }
+        return detail::npy_api::get().PyArray_FromAny_(
+            ptr, dtype::of<T>().release().ptr(), 0, 0,
+            detail::npy_api::NPY_ARRAY_ENSUREARRAY_ | ExtraFlags, nullptr);
+    }
+};
+
+template <typename T>
+struct format_descriptor<T, detail::enable_if_t<detail::is_pod_struct<T>::value>> {
+    static std::string format() {
+        return detail::npy_format_descriptor<typename std::remove_cv<T>::type>::format();
+    }
+};
+
+template <size_t N> struct format_descriptor<char[N]> {
+    static std::string format() { return std::to_string(N) + "s"; }
+};
+template <size_t N> struct format_descriptor<std::array<char, N>> {
+    static std::string format() { return std::to_string(N) + "s"; }
+};
+
+template <typename T>
+struct format_descriptor<T, detail::enable_if_t<std::is_enum<T>::value>> {
+    static std::string format() {
+        return format_descriptor<
+            typename std::remove_cv<typename std::underlying_type<T>::type>::type>::format();
+    }
+};
+
+template <typename T>
+struct format_descriptor<T, detail::enable_if_t<detail::array_info<T>::is_array>> {
+    static std::string format() {
+        using detail::_;
+        static constexpr auto extents = _("(") + detail::array_info<T>::extents + _(")");
+        return extents.text + format_descriptor<detail::remove_all_extents_t<T>>::format();
+    }
+};
+
+NAMESPACE_BEGIN(detail)
+template <typename T, int ExtraFlags>
+struct pyobject_caster<array_t<T, ExtraFlags>> {
+    using type = array_t<T, ExtraFlags>;
+
+    bool load(handle src, bool convert) {
+        if (!convert && !type::check_(src))
+            return false;
+        value = type::ensure(src);
+        return static_cast<bool>(value);
+    }
+
+    static handle cast(const handle &src, return_value_policy /* policy */, handle /* parent */) {
+        return src.inc_ref();
+    }
+    PYBIND11_TYPE_CASTER(type, handle_type_name<type>::name);
+};
+
+template <typename T>
+struct compare_buffer_info<T, detail::enable_if_t<detail::is_pod_struct<T>::value>> {
+    static bool compare(const buffer_info& b) {
+        return npy_api::get().PyArray_EquivTypes_(dtype::of<T>().ptr(), dtype(b).ptr());
+    }
+};
+
+template <typename T, typename = void>
+struct npy_format_descriptor_name;
+
+template <typename T>
+struct npy_format_descriptor_name<T, enable_if_t<std::is_integral<T>::value>> {
+    static constexpr auto name = _<std::is_same<T, bool>::value>(
+        _("bool"), _<std::is_signed<T>::value>("int", "uint") + _<sizeof(T)*8>()
+    );
+};
+
+template <typename T>
+struct npy_format_descriptor_name<T, enable_if_t<std::is_floating_point<T>::value>> {
+    static constexpr auto name = _<std::is_same<T, float>::value || std::is_same<T, double>::value>(
+        _("float") + _<sizeof(T)*8>(), _("longdouble")
+    );
+};
+
+template <typename T>
+struct npy_format_descriptor_name<T, enable_if_t<is_complex<T>::value>> {
+    static constexpr auto name = _<std::is_same<typename T::value_type, float>::value
+                                   || std::is_same<typename T::value_type, double>::value>(
+        _("complex") + _<sizeof(typename T::value_type)*16>(), _("longcomplex")
+    );
+};
+
+template <typename T>
+struct npy_format_descriptor<T, enable_if_t<satisfies_any_of<T, std::is_arithmetic, is_complex>::value>>
+    : npy_format_descriptor_name<T> {
+private:
+    // NB: the order here must match the one in common.h
+    constexpr static const int values[15] = {
+        npy_api::NPY_BOOL_,
+        npy_api::NPY_BYTE_,   npy_api::NPY_UBYTE_,   npy_api::NPY_SHORT_,    npy_api::NPY_USHORT_,
+        npy_api::NPY_INT_,    npy_api::NPY_UINT_,    npy_api::NPY_LONGLONG_, npy_api::NPY_ULONGLONG_,
+        npy_api::NPY_FLOAT_,  npy_api::NPY_DOUBLE_,  npy_api::NPY_LONGDOUBLE_,
+        npy_api::NPY_CFLOAT_, npy_api::NPY_CDOUBLE_, npy_api::NPY_CLONGDOUBLE_
+    };
+
+public:
+    static constexpr int value = values[detail::is_fmt_numeric<T>::index];
+
+    static pybind11::dtype dtype() {
+        if (auto ptr = npy_api::get().PyArray_DescrFromType_(value))
+            return reinterpret_borrow<pybind11::dtype>(ptr);
+        pybind11_fail("Unsupported buffer format!");
+    }
+};
+
+#define PYBIND11_DECL_CHAR_FMT \
+    static constexpr auto name = _("S") + _<N>(); \
+    static pybind11::dtype dtype() { return pybind11::dtype(std::string("S") + std::to_string(N)); }
+template <size_t N> struct npy_format_descriptor<char[N]> { PYBIND11_DECL_CHAR_FMT };
+template <size_t N> struct npy_format_descriptor<std::array<char, N>> { PYBIND11_DECL_CHAR_FMT };
+#undef PYBIND11_DECL_CHAR_FMT
+
+template<typename T> struct npy_format_descriptor<T, enable_if_t<array_info<T>::is_array>> {
+private:
+    using base_descr = npy_format_descriptor<typename array_info<T>::type>;
+public:
+    static_assert(!array_info<T>::is_empty, "Zero-sized arrays are not supported");
+
+    static constexpr auto name = _("(") + array_info<T>::extents + _(")") + base_descr::name;
+    static pybind11::dtype dtype() {
+        list shape;
+        array_info<T>::append_extents(shape);
+        return pybind11::dtype::from_args(pybind11::make_tuple(base_descr::dtype(), shape));
+    }
+};
+
+template<typename T> struct npy_format_descriptor<T, enable_if_t<std::is_enum<T>::value>> {
+private:
+    using base_descr = npy_format_descriptor<typename std::underlying_type<T>::type>;
+public:
+    static constexpr auto name = base_descr::name;
+    static pybind11::dtype dtype() { return base_descr::dtype(); }
+};
+
+struct field_descriptor {
+    const char *name;
+    ssize_t offset;
+    ssize_t size;
+    std::string format;
+    dtype descr;
+};
+
+inline PYBIND11_NOINLINE void register_structured_dtype(
+    const std::initializer_list<field_descriptor>& fields,
+    const std::type_info& tinfo, ssize_t itemsize,
+    bool (*direct_converter)(PyObject *, void *&)) {
+
+    auto& numpy_internals = get_numpy_internals();
+    if (numpy_internals.get_type_info(tinfo, false))
+        pybind11_fail("NumPy: dtype is already registered");
+
+    list names, formats, offsets;
+    for (auto field : fields) {
+        if (!field.descr)
+            pybind11_fail(std::string("NumPy: unsupported field dtype: `") +
+                            field.name + "` @ " + tinfo.name());
+        names.append(PYBIND11_STR_TYPE(field.name));
+        formats.append(field.descr);
+        offsets.append(pybind11::int_(field.offset));
+    }
+    auto dtype_ptr = pybind11::dtype(names, formats, offsets, itemsize).release().ptr();
+
+    // There is an existing bug in NumPy (as of v1.11): trailing bytes are
+    // not encoded explicitly into the format string. This will supposedly
+    // get fixed in v1.12; for further details, see these:
+    // - https://github.com/numpy/numpy/issues/7797
+    // - https://github.com/numpy/numpy/pull/7798
+    // Because of this, we won't use numpy's logic to generate buffer format
+    // strings and will just do it ourselves.
+    std::vector<field_descriptor> ordered_fields(fields);
+    std::sort(ordered_fields.begin(), ordered_fields.end(),
+        [](const field_descriptor &a, const field_descriptor &b) { return a.offset < b.offset; });
+    ssize_t offset = 0;
+    std::ostringstream oss;
+    // mark the structure as unaligned with '^', because numpy and C++ don't
+    // always agree about alignment (particularly for complex), and we're
+    // explicitly listing all our padding. This depends on none of the fields
+    // overriding the endianness. Putting the ^ in front of individual fields
+    // isn't guaranteed to work due to https://github.com/numpy/numpy/issues/9049
+    oss << "^T{";
+    for (auto& field : ordered_fields) {
+        if (field.offset > offset)
+            oss << (field.offset - offset) << 'x';
+        oss << field.format << ':' << field.name << ':';
+        offset = field.offset + field.size;
+    }
+    if (itemsize > offset)
+        oss << (itemsize - offset) << 'x';
+    oss << '}';
+    auto format_str = oss.str();
+
+    // Sanity check: verify that NumPy properly parses our buffer format string
+    auto& api = npy_api::get();
+    auto arr =  array(buffer_info(nullptr, itemsize, format_str, 1));
+    if (!api.PyArray_EquivTypes_(dtype_ptr, arr.dtype().ptr()))
+        pybind11_fail("NumPy: invalid buffer descriptor!");
+
+    auto tindex = std::type_index(tinfo);
+    numpy_internals.registered_dtypes[tindex] = { dtype_ptr, format_str };
+    get_internals().direct_conversions[tindex].push_back(direct_converter);
+}
+
+template <typename T, typename SFINAE> struct npy_format_descriptor {
+    static_assert(is_pod_struct<T>::value, "Attempt to use a non-POD or unimplemented POD type as a numpy dtype");
+
+    static constexpr auto name = make_caster<T>::name;
+
+    static pybind11::dtype dtype() {
+        return reinterpret_borrow<pybind11::dtype>(dtype_ptr());
+    }
+
+    static std::string format() {
+        static auto format_str = get_numpy_internals().get_type_info<T>(true)->format_str;
+        return format_str;
+    }
+
+    static void register_dtype(const std::initializer_list<field_descriptor>& fields) {
+        register_structured_dtype(fields, typeid(typename std::remove_cv<T>::type),
+                                  sizeof(T), &direct_converter);
+    }
+
+private:
+    static PyObject* dtype_ptr() {
+        static PyObject* ptr = get_numpy_internals().get_type_info<T>(true)->dtype_ptr;
+        return ptr;
+    }
+
+    static bool direct_converter(PyObject *obj, void*& value) {
+        auto& api = npy_api::get();
+        if (!PyObject_TypeCheck(obj, api.PyVoidArrType_Type_))
+            return false;
+        if (auto descr = reinterpret_steal<object>(api.PyArray_DescrFromScalar_(obj))) {
+            if (api.PyArray_EquivTypes_(dtype_ptr(), descr.ptr())) {
+                value = ((PyVoidScalarObject_Proxy *) obj)->obval;
+                return true;
+            }
+        }
+        return false;
+    }
+};
+
+#ifdef __CLION_IDE__ // replace heavy macro with dummy code for the IDE (doesn't affect code)
+# define PYBIND11_NUMPY_DTYPE(Type, ...) ((void)0)
+# define PYBIND11_NUMPY_DTYPE_EX(Type, ...) ((void)0)
+#else
+
+#define PYBIND11_FIELD_DESCRIPTOR_EX(T, Field, Name)                                          \
+    ::pybind11::detail::field_descriptor {                                                    \
+        Name, offsetof(T, Field), sizeof(decltype(std::declval<T>().Field)),                  \
+        ::pybind11::format_descriptor<decltype(std::declval<T>().Field)>::format(),           \
+        ::pybind11::detail::npy_format_descriptor<decltype(std::declval<T>().Field)>::dtype() \
+    }
+
+// Extract name, offset and format descriptor for a struct field
+#define PYBIND11_FIELD_DESCRIPTOR(T, Field) PYBIND11_FIELD_DESCRIPTOR_EX(T, Field, #Field)
+
+// The main idea of this macro is borrowed from https://github.com/swansontec/map-macro
+// (C) William Swanson, Paul Fultz
+#define PYBIND11_EVAL0(...) __VA_ARGS__
+#define PYBIND11_EVAL1(...) PYBIND11_EVAL0 (PYBIND11_EVAL0 (PYBIND11_EVAL0 (__VA_ARGS__)))
+#define PYBIND11_EVAL2(...) PYBIND11_EVAL1 (PYBIND11_EVAL1 (PYBIND11_EVAL1 (__VA_ARGS__)))
+#define PYBIND11_EVAL3(...) PYBIND11_EVAL2 (PYBIND11_EVAL2 (PYBIND11_EVAL2 (__VA_ARGS__)))
+#define PYBIND11_EVAL4(...) PYBIND11_EVAL3 (PYBIND11_EVAL3 (PYBIND11_EVAL3 (__VA_ARGS__)))
+#define PYBIND11_EVAL(...)  PYBIND11_EVAL4 (PYBIND11_EVAL4 (PYBIND11_EVAL4 (__VA_ARGS__)))
+#define PYBIND11_MAP_END(...)
+#define PYBIND11_MAP_OUT
+#define PYBIND11_MAP_COMMA ,
+#define PYBIND11_MAP_GET_END() 0, PYBIND11_MAP_END
+#define PYBIND11_MAP_NEXT0(test, next, ...) next PYBIND11_MAP_OUT
+#define PYBIND11_MAP_NEXT1(test, next) PYBIND11_MAP_NEXT0 (test, next, 0)
+#define PYBIND11_MAP_NEXT(test, next)  PYBIND11_MAP_NEXT1 (PYBIND11_MAP_GET_END test, next)
+#ifdef _MSC_VER // MSVC is not as eager to expand macros, hence this workaround
+#define PYBIND11_MAP_LIST_NEXT1(test, next) \
+    PYBIND11_EVAL0 (PYBIND11_MAP_NEXT0 (test, PYBIND11_MAP_COMMA next, 0))
+#else
+#define PYBIND11_MAP_LIST_NEXT1(test, next) \
+    PYBIND11_MAP_NEXT0 (test, PYBIND11_MAP_COMMA next, 0)
+#endif
+#define PYBIND11_MAP_LIST_NEXT(test, next) \
+    PYBIND11_MAP_LIST_NEXT1 (PYBIND11_MAP_GET_END test, next)
+#define PYBIND11_MAP_LIST0(f, t, x, peek, ...) \
+    f(t, x) PYBIND11_MAP_LIST_NEXT (peek, PYBIND11_MAP_LIST1) (f, t, peek, __VA_ARGS__)
+#define PYBIND11_MAP_LIST1(f, t, x, peek, ...) \
+    f(t, x) PYBIND11_MAP_LIST_NEXT (peek, PYBIND11_MAP_LIST0) (f, t, peek, __VA_ARGS__)
+// PYBIND11_MAP_LIST(f, t, a1, a2, ...) expands to f(t, a1), f(t, a2), ...
+#define PYBIND11_MAP_LIST(f, t, ...) \
+    PYBIND11_EVAL (PYBIND11_MAP_LIST1 (f, t, __VA_ARGS__, (), 0))
+
+#define PYBIND11_NUMPY_DTYPE(Type, ...) \
+    ::pybind11::detail::npy_format_descriptor<Type>::register_dtype \
+        ({PYBIND11_MAP_LIST (PYBIND11_FIELD_DESCRIPTOR, Type, __VA_ARGS__)})
+
+#ifdef _MSC_VER
+#define PYBIND11_MAP2_LIST_NEXT1(test, next) \
+    PYBIND11_EVAL0 (PYBIND11_MAP_NEXT0 (test, PYBIND11_MAP_COMMA next, 0))
+#else
+#define PYBIND11_MAP2_LIST_NEXT1(test, next) \
+    PYBIND11_MAP_NEXT0 (test, PYBIND11_MAP_COMMA next, 0)
+#endif
+#define PYBIND11_MAP2_LIST_NEXT(test, next) \
+    PYBIND11_MAP2_LIST_NEXT1 (PYBIND11_MAP_GET_END test, next)
+#define PYBIND11_MAP2_LIST0(f, t, x1, x2, peek, ...) \
+    f(t, x1, x2) PYBIND11_MAP2_LIST_NEXT (peek, PYBIND11_MAP2_LIST1) (f, t, peek, __VA_ARGS__)
+#define PYBIND11_MAP2_LIST1(f, t, x1, x2, peek, ...) \
+    f(t, x1, x2) PYBIND11_MAP2_LIST_NEXT (peek, PYBIND11_MAP2_LIST0) (f, t, peek, __VA_ARGS__)
+// PYBIND11_MAP2_LIST(f, t, a1, a2, ...) expands to f(t, a1, a2), f(t, a3, a4), ...
+#define PYBIND11_MAP2_LIST(f, t, ...) \
+    PYBIND11_EVAL (PYBIND11_MAP2_LIST1 (f, t, __VA_ARGS__, (), 0))
+
+#define PYBIND11_NUMPY_DTYPE_EX(Type, ...) \
+    ::pybind11::detail::npy_format_descriptor<Type>::register_dtype \
+        ({PYBIND11_MAP2_LIST (PYBIND11_FIELD_DESCRIPTOR_EX, Type, __VA_ARGS__)})
+
+#endif // __CLION_IDE__
+
+template  <class T>
+using array_iterator = typename std::add_pointer<T>::type;
+
+template <class T>
+array_iterator<T> array_begin(const buffer_info& buffer) {
+    return array_iterator<T>(reinterpret_cast<T*>(buffer.ptr));
+}
+
+template <class T>
+array_iterator<T> array_end(const buffer_info& buffer) {
+    return array_iterator<T>(reinterpret_cast<T*>(buffer.ptr) + buffer.size);
+}
+
+class common_iterator {
+public:
+    using container_type = std::vector<ssize_t>;
+    using value_type = container_type::value_type;
+    using size_type = container_type::size_type;
+
+    common_iterator() : p_ptr(0), m_strides() {}
+
+    common_iterator(void* ptr, const container_type& strides, const container_type& shape)
+        : p_ptr(reinterpret_cast<char*>(ptr)), m_strides(strides.size()) {
+        m_strides.back() = static_cast<value_type>(strides.back());
+        for (size_type i = m_strides.size() - 1; i != 0; --i) {
+            size_type j = i - 1;
+            value_type s = static_cast<value_type>(shape[i]);
+            m_strides[j] = strides[j] + m_strides[i] - strides[i] * s;
+        }
+    }
+
+    void increment(size_type dim) {
+        p_ptr += m_strides[dim];
+    }
+
+    void* data() const {
+        return p_ptr;
+    }
+
+private:
+    char* p_ptr;
+    container_type m_strides;
+};
+
+template <size_t N> class multi_array_iterator {
+public:
+    using container_type = std::vector<ssize_t>;
+
+    multi_array_iterator(const std::array<buffer_info, N> &buffers,
+                         const container_type &shape)
+        : m_shape(shape.size()), m_index(shape.size(), 0),
+          m_common_iterator() {
+
+        // Manual copy to avoid conversion warning if using std::copy
+        for (size_t i = 0; i < shape.size(); ++i)
+            m_shape[i] = shape[i];
+
+        container_type strides(shape.size());
+        for (size_t i = 0; i < N; ++i)
+            init_common_iterator(buffers[i], shape, m_common_iterator[i], strides);
+    }
+
+    multi_array_iterator& operator++() {
+        for (size_t j = m_index.size(); j != 0; --j) {
+            size_t i = j - 1;
+            if (++m_index[i] != m_shape[i]) {
+                increment_common_iterator(i);
+                break;
+            } else {
+                m_index[i] = 0;
+            }
+        }
+        return *this;
+    }
+
+    template <size_t K, class T = void> T* data() const {
+        return reinterpret_cast<T*>(m_common_iterator[K].data());
+    }
+
+private:
+
+    using common_iter = common_iterator;
+
+    void init_common_iterator(const buffer_info &buffer,
+                              const container_type &shape,
+                              common_iter &iterator,
+                              container_type &strides) {
+        auto buffer_shape_iter = buffer.shape.rbegin();
+        auto buffer_strides_iter = buffer.strides.rbegin();
+        auto shape_iter = shape.rbegin();
+        auto strides_iter = strides.rbegin();
+
+        while (buffer_shape_iter != buffer.shape.rend()) {
+            if (*shape_iter == *buffer_shape_iter)
+                *strides_iter = *buffer_strides_iter;
+            else
+                *strides_iter = 0;
+
+            ++buffer_shape_iter;
+            ++buffer_strides_iter;
+            ++shape_iter;
+            ++strides_iter;
+        }
+
+        std::fill(strides_iter, strides.rend(), 0);
+        iterator = common_iter(buffer.ptr, strides, shape);
+    }
+
+    void increment_common_iterator(size_t dim) {
+        for (auto &iter : m_common_iterator)
+            iter.increment(dim);
+    }
+
+    container_type m_shape;
+    container_type m_index;
+    std::array<common_iter, N> m_common_iterator;
+};
+
+enum class broadcast_trivial { non_trivial, c_trivial, f_trivial };
+
+// Populates the shape and number of dimensions for the set of buffers.  Returns a broadcast_trivial
+// enum value indicating whether the broadcast is "trivial"--that is, has each buffer being either a
+// singleton or a full-size, C-contiguous (`c_trivial`) or Fortran-contiguous (`f_trivial`) storage
+// buffer; returns `non_trivial` otherwise.
+template <size_t N>
+broadcast_trivial broadcast(const std::array<buffer_info, N> &buffers, ssize_t &ndim, std::vector<ssize_t> &shape) {
+    ndim = std::accumulate(buffers.begin(), buffers.end(), ssize_t(0), [](ssize_t res, const buffer_info &buf) {
+        return std::max(res, buf.ndim);
+    });
+
+    shape.clear();
+    shape.resize((size_t) ndim, 1);
+
+    // Figure out the output size, and make sure all input arrays conform (i.e. are either size 1 or
+    // the full size).
+    for (size_t i = 0; i < N; ++i) {
+        auto res_iter = shape.rbegin();
+        auto end = buffers[i].shape.rend();
+        for (auto shape_iter = buffers[i].shape.rbegin(); shape_iter != end; ++shape_iter, ++res_iter) {
+            const auto &dim_size_in = *shape_iter;
+            auto &dim_size_out = *res_iter;
+
+            // Each input dimension can either be 1 or `n`, but `n` values must match across buffers
+            if (dim_size_out == 1)
+                dim_size_out = dim_size_in;
+            else if (dim_size_in != 1 && dim_size_in != dim_size_out)
+                pybind11_fail("pybind11::vectorize: incompatible size/dimension of inputs!");
+        }
+    }
+
+    bool trivial_broadcast_c = true;
+    bool trivial_broadcast_f = true;
+    for (size_t i = 0; i < N && (trivial_broadcast_c || trivial_broadcast_f); ++i) {
+        if (buffers[i].size == 1)
+            continue;
+
+        // Require the same number of dimensions:
+        if (buffers[i].ndim != ndim)
+            return broadcast_trivial::non_trivial;
+
+        // Require all dimensions be full-size:
+        if (!std::equal(buffers[i].shape.cbegin(), buffers[i].shape.cend(), shape.cbegin()))
+            return broadcast_trivial::non_trivial;
+
+        // Check for C contiguity (but only if previous inputs were also C contiguous)
+        if (trivial_broadcast_c) {
+            ssize_t expect_stride = buffers[i].itemsize;
+            auto end = buffers[i].shape.crend();
+            for (auto shape_iter = buffers[i].shape.crbegin(), stride_iter = buffers[i].strides.crbegin();
+                    trivial_broadcast_c && shape_iter != end; ++shape_iter, ++stride_iter) {
+                if (expect_stride == *stride_iter)
+                    expect_stride *= *shape_iter;
+                else
+                    trivial_broadcast_c = false;
+            }
+        }
+
+        // Check for Fortran contiguity (if previous inputs were also F contiguous)
+        if (trivial_broadcast_f) {
+            ssize_t expect_stride = buffers[i].itemsize;
+            auto end = buffers[i].shape.cend();
+            for (auto shape_iter = buffers[i].shape.cbegin(), stride_iter = buffers[i].strides.cbegin();
+                    trivial_broadcast_f && shape_iter != end; ++shape_iter, ++stride_iter) {
+                if (expect_stride == *stride_iter)
+                    expect_stride *= *shape_iter;
+                else
+                    trivial_broadcast_f = false;
+            }
+        }
+    }
+
+    return
+        trivial_broadcast_c ? broadcast_trivial::c_trivial :
+        trivial_broadcast_f ? broadcast_trivial::f_trivial :
+        broadcast_trivial::non_trivial;
+}
+
+template <typename T>
+struct vectorize_arg {
+    static_assert(!std::is_rvalue_reference<T>::value, "Functions with rvalue reference arguments cannot be vectorized");
+    // The wrapped function gets called with this type:
+    using call_type = remove_reference_t<T>;
+    // Is this a vectorized argument?
+    static constexpr bool vectorize =
+        satisfies_any_of<call_type, std::is_arithmetic, is_complex, std::is_pod>::value &&
+        satisfies_none_of<call_type, std::is_pointer, std::is_array, is_std_array, std::is_enum>::value &&
+        (!std::is_reference<T>::value ||
+         (std::is_lvalue_reference<T>::value && std::is_const<call_type>::value));
+    // Accept this type: an array for vectorized types, otherwise the type as-is:
+    using type = conditional_t<vectorize, array_t<remove_cv_t<call_type>, array::forcecast>, T>;
+};
+
+template <typename Func, typename Return, typename... Args>
+struct vectorize_helper {
+private:
+    static constexpr size_t N = sizeof...(Args);
+    static constexpr size_t NVectorized = constexpr_sum(vectorize_arg<Args>::vectorize...);
+    static_assert(NVectorized >= 1,
+            "pybind11::vectorize(...) requires a function with at least one vectorizable argument");
+
+public:
+    template <typename T>
+    explicit vectorize_helper(T &&f) : f(std::forward<T>(f)) { }
+
+    object operator()(typename vectorize_arg<Args>::type... args) {
+        return run(args...,
+                   make_index_sequence<N>(),
+                   select_indices<vectorize_arg<Args>::vectorize...>(),
+                   make_index_sequence<NVectorized>());
+    }
+
+private:
+    remove_reference_t<Func> f;
+
+    template <size_t Index> using param_n_t = typename pack_element<Index, typename vectorize_arg<Args>::call_type...>::type;
+
+    // Runs a vectorized function given arguments tuple and three index sequences:
+    //     - Index is the full set of 0 ... (N-1) argument indices;
+    //     - VIndex is the subset of argument indices with vectorized parameters, letting us access
+    //       vectorized arguments (anything not in this sequence is passed through)
+    //     - BIndex is a incremental sequence (beginning at 0) of the same size as VIndex, so that
+    //       we can store vectorized buffer_infos in an array (argument VIndex has its buffer at
+    //       index BIndex in the array).
+    template <size_t... Index, size_t... VIndex, size_t... BIndex> object run(
+            typename vectorize_arg<Args>::type &...args,
+            index_sequence<Index...> i_seq, index_sequence<VIndex...> vi_seq, index_sequence<BIndex...> bi_seq) {
+
+        // Pointers to values the function was called with; the vectorized ones set here will start
+        // out as array_t<T> pointers, but they will be changed them to T pointers before we make
+        // call the wrapped function.  Non-vectorized pointers are left as-is.
+        std::array<void *, N> params{{ &args... }};
+
+        // The array of `buffer_info`s of vectorized arguments:
+        std::array<buffer_info, NVectorized> buffers{{ reinterpret_cast<array *>(params[VIndex])->request()... }};
+
+        /* Determine dimensions parameters of output array */
+        ssize_t nd = 0;
+        std::vector<ssize_t> shape(0);
+        auto trivial = broadcast(buffers, nd, shape);
+        size_t ndim = (size_t) nd;
+
+        size_t size = std::accumulate(shape.begin(), shape.end(), (size_t) 1, std::multiplies<size_t>());
+
+        // If all arguments are 0-dimension arrays (i.e. single values) return a plain value (i.e.
+        // not wrapped in an array).
+        if (size == 1 && ndim == 0) {
+            PYBIND11_EXPAND_SIDE_EFFECTS(params[VIndex] = buffers[BIndex].ptr);
+            return cast(f(*reinterpret_cast<param_n_t<Index> *>(params[Index])...));
+        }
+
+        array_t<Return> result;
+        if (trivial == broadcast_trivial::f_trivial) result = array_t<Return, array::f_style>(shape);
+        else result = array_t<Return>(shape);
+
+        if (size == 0) return result;
+
+        /* Call the function */
+        if (trivial == broadcast_trivial::non_trivial)
+            apply_broadcast(buffers, params, result, i_seq, vi_seq, bi_seq);
+        else
+            apply_trivial(buffers, params, result.mutable_data(), size, i_seq, vi_seq, bi_seq);
+
+        return result;
+    }
+
+    template <size_t... Index, size_t... VIndex, size_t... BIndex>
+    void apply_trivial(std::array<buffer_info, NVectorized> &buffers,
+                       std::array<void *, N> &params,
+                       Return *out,
+                       size_t size,
+                       index_sequence<Index...>, index_sequence<VIndex...>, index_sequence<BIndex...>) {
+
+        // Initialize an array of mutable byte references and sizes with references set to the
+        // appropriate pointer in `params`; as we iterate, we'll increment each pointer by its size
+        // (except for singletons, which get an increment of 0).
+        std::array<std::pair<unsigned char *&, const size_t>, NVectorized> vecparams{{
+            std::pair<unsigned char *&, const size_t>(
+                    reinterpret_cast<unsigned char *&>(params[VIndex] = buffers[BIndex].ptr),
+                    buffers[BIndex].size == 1 ? 0 : sizeof(param_n_t<VIndex>)
+            )...
+        }};
+
+        for (size_t i = 0; i < size; ++i) {
+            out[i] = f(*reinterpret_cast<param_n_t<Index> *>(params[Index])...);
+            for (auto &x : vecparams) x.first += x.second;
+        }
+    }
+
+    template <size_t... Index, size_t... VIndex, size_t... BIndex>
+    void apply_broadcast(std::array<buffer_info, NVectorized> &buffers,
+                         std::array<void *, N> &params,
+                         array_t<Return> &output_array,
+                         index_sequence<Index...>, index_sequence<VIndex...>, index_sequence<BIndex...>) {
+
+        buffer_info output = output_array.request();
+        multi_array_iterator<NVectorized> input_iter(buffers, output.shape);
+
+        for (array_iterator<Return> iter = array_begin<Return>(output), end = array_end<Return>(output);
+             iter != end;
+             ++iter, ++input_iter) {
+            PYBIND11_EXPAND_SIDE_EFFECTS((
+                params[VIndex] = input_iter.template data<BIndex>()
+            ));
+            *iter = f(*reinterpret_cast<param_n_t<Index> *>(std::get<Index>(params))...);
+        }
+    }
+};
+
+template <typename Func, typename Return, typename... Args>
+vectorize_helper<Func, Return, Args...>
+vectorize_extractor(const Func &f, Return (*) (Args ...)) {
+    return detail::vectorize_helper<Func, Return, Args...>(f);
+}
+
+template <typename T, int Flags> struct handle_type_name<array_t<T, Flags>> {
+    static constexpr auto name = _("numpy.ndarray[") + npy_format_descriptor<T>::name + _("]");
+};
+
+NAMESPACE_END(detail)
+
+// Vanilla pointer vectorizer:
+template <typename Return, typename... Args>
+detail::vectorize_helper<Return (*)(Args...), Return, Args...>
+vectorize(Return (*f) (Args ...)) {
+    return detail::vectorize_helper<Return (*)(Args...), Return, Args...>(f);
+}
+
+// lambda vectorizer:
+template <typename Func, detail::enable_if_t<detail::is_lambda<Func>::value, int> = 0>
+auto vectorize(Func &&f) -> decltype(
+        detail::vectorize_extractor(std::forward<Func>(f), (detail::function_signature_t<Func> *) nullptr)) {
+    return detail::vectorize_extractor(std::forward<Func>(f), (detail::function_signature_t<Func> *) nullptr);
+}
+
+// Vectorize a class method (non-const):
+template <typename Return, typename Class, typename... Args,
+          typename Helper = detail::vectorize_helper<decltype(std::mem_fn(std::declval<Return (Class::*)(Args...)>())), Return, Class *, Args...>>
+Helper vectorize(Return (Class::*f)(Args...)) {
+    return Helper(std::mem_fn(f));
+}
+
+// Vectorize a class method (non-const):
+template <typename Return, typename Class, typename... Args,
+          typename Helper = detail::vectorize_helper<decltype(std::mem_fn(std::declval<Return (Class::*)(Args...) const>())), Return, const Class *, Args...>>
+Helper vectorize(Return (Class::*f)(Args...) const) {
+    return Helper(std::mem_fn(f));
+}
+
+NAMESPACE_END(PYBIND11_NAMESPACE)
+
+#if defined(_MSC_VER)
+#pragma warning(pop)
+#endif

dlib/external/pybind11/include/pybind11/operators.h

+/*
+    pybind11/operator.h: Metatemplates for operator overloading
+
+    Copyright (c) 2016 Wenzel Jakob <wenzel.jakob@epfl.ch>
+
+    All rights reserved. Use of this source code is governed by a
+    BSD-style license that can be found in the LICENSE file.
+*/
+
+#pragma once
+
+#include "pybind11.h"
+
+#if defined(__clang__) && !defined(__INTEL_COMPILER)
+#  pragma clang diagnostic ignored "-Wunsequenced" // multiple unsequenced modifications to 'self' (when using def(py::self OP Type()))
+#elif defined(_MSC_VER)
+#  pragma warning(push)
+#  pragma warning(disable: 4127) // warning C4127: Conditional expression is constant
+#endif
+
+NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
+NAMESPACE_BEGIN(detail)
+
+/// Enumeration with all supported operator types
+enum op_id : int {
+    op_add, op_sub, op_mul, op_div, op_mod, op_divmod, op_pow, op_lshift,
+    op_rshift, op_and, op_xor, op_or, op_neg, op_pos, op_abs, op_invert,
+    op_int, op_long, op_float, op_str, op_cmp, op_gt, op_ge, op_lt, op_le,
+    op_eq, op_ne, op_iadd, op_isub, op_imul, op_idiv, op_imod, op_ilshift,
+    op_irshift, op_iand, op_ixor, op_ior, op_complex, op_bool, op_nonzero,
+    op_repr, op_truediv, op_itruediv, op_hash
+};
+
+enum op_type : int {
+    op_l, /* base type on left */
+    op_r, /* base type on right */
+    op_u  /* unary operator */
+};
+
+struct self_t { };
+static const self_t self = self_t();
+
+/// Type for an unused type slot
+struct undefined_t { };
+
+/// Don't warn about an unused variable
+inline self_t __self() { return self; }
+
+/// base template of operator implementations
+template <op_id, op_type, typename B, typename L, typename R> struct op_impl { };
+
+/// Operator implementation generator
+template <op_id id, op_type ot, typename L, typename R> struct op_ {
+    template <typename Class, typename... Extra> void execute(Class &cl, const Extra&... extra) const {
+        using Base = typename Class::type;
+        using L_type = conditional_t<std::is_same<L, self_t>::value, Base, L>;
+        using R_type = conditional_t<std::is_same<R, self_t>::value, Base, R>;
+        using op = op_impl<id, ot, Base, L_type, R_type>;
+        cl.def(op::name(), &op::execute, is_operator(), extra...);
+        #if PY_MAJOR_VERSION < 3
+        if (id == op_truediv || id == op_itruediv)
+            cl.def(id == op_itruediv ? "__idiv__" : ot == op_l ? "__div__" : "__rdiv__",
+                    &op::execute, is_operator(), extra...);
+        #endif
+    }
+    template <typename Class, typename... Extra> void execute_cast(Class &cl, const Extra&... extra) const {
+        using Base = typename Class::type;
+        using L_type = conditional_t<std::is_same<L, self_t>::value, Base, L>;
+        using R_type = conditional_t<std::is_same<R, self_t>::value, Base, R>;
+        using op = op_impl<id, ot, Base, L_type, R_type>;
+        cl.def(op::name(), &op::execute_cast, is_operator(), extra...);
+        #if PY_MAJOR_VERSION < 3
+        if (id == op_truediv || id == op_itruediv)
+            cl.def(id == op_itruediv ? "__idiv__" : ot == op_l ? "__div__" : "__rdiv__",
+                    &op::execute, is_operator(), extra...);
+        #endif
+    }
+};
+
+#define PYBIND11_BINARY_OPERATOR(id, rid, op, expr)                                    \
+template <typename B, typename L, typename R> struct op_impl<op_##id, op_l, B, L, R> { \
+    static char const* name() { return "__" #id "__"; }                                \
+    static auto execute(const L &l, const R &r) -> decltype(expr) { return (expr); }   \
+    static B execute_cast(const L &l, const R &r) { return B(expr); }                  \
+};                                                                                     \
+template <typename B, typename L, typename R> struct op_impl<op_##id, op_r, B, L, R> { \
+    static char const* name() { return "__" #rid "__"; }                               \
+    static auto execute(const R &r, const L &l) -> decltype(expr) { return (expr); }   \
+    static B execute_cast(const R &r, const L &l) { return B(expr); }                  \
+};                                                                                     \
+inline op_<op_##id, op_l, self_t, self_t> op(const self_t &, const self_t &) {         \
+    return op_<op_##id, op_l, self_t, self_t>();                                       \
+}                                                                                      \
+template <typename T> op_<op_##id, op_l, self_t, T> op(const self_t &, const T &) {    \
+    return op_<op_##id, op_l, self_t, T>();                                            \
+}                                                                                      \
+template <typename T> op_<op_##id, op_r, T, self_t> op(const T &, const self_t &) {    \
+    return op_<op_##id, op_r, T, self_t>();                                            \
+}
+
+#define PYBIND11_INPLACE_OPERATOR(id, op, expr)                                        \
+template <typename B, typename L, typename R> struct op_impl<op_##id, op_l, B, L, R> { \
+    static char const* name() { return "__" #id "__"; }                                \
+    static auto execute(L &l, const R &r) -> decltype(expr) { return expr; }           \
+    static B execute_cast(L &l, const R &r) { return B(expr); }                        \
+};                                                                                     \
+template <typename T> op_<op_##id, op_l, self_t, T> op(const self_t &, const T &) {    \
+    return op_<op_##id, op_l, self_t, T>();                                            \
+}
+
+#define PYBIND11_UNARY_OPERATOR(id, op, expr)                                          \
+template <typename B, typename L> struct op_impl<op_##id, op_u, B, L, undefined_t> {   \
+    static char const* name() { return "__" #id "__"; }                                \
+    static auto execute(const L &l) -> decltype(expr) { return expr; }                 \
+    static B execute_cast(const L &l) { return B(expr); }                              \
+};                                                                                     \
+inline op_<op_##id, op_u, self_t, undefined_t> op(const self_t &) {                    \
+    return op_<op_##id, op_u, self_t, undefined_t>();                                  \
+}
+
+PYBIND11_BINARY_OPERATOR(sub,       rsub,         operator-,    l - r)
+PYBIND11_BINARY_OPERATOR(add,       radd,         operator+,    l + r)
+PYBIND11_BINARY_OPERATOR(mul,       rmul,         operator*,    l * r)
+PYBIND11_BINARY_OPERATOR(truediv,   rtruediv,     operator/,    l / r)
+PYBIND11_BINARY_OPERATOR(mod,       rmod,         operator%,    l % r)
+PYBIND11_BINARY_OPERATOR(lshift,    rlshift,      operator<<,   l << r)
+PYBIND11_BINARY_OPERATOR(rshift,    rrshift,      operator>>,   l >> r)
+PYBIND11_BINARY_OPERATOR(and,       rand,         operator&,    l & r)
+PYBIND11_BINARY_OPERATOR(xor,       rxor,         operator^,    l ^ r)
+PYBIND11_BINARY_OPERATOR(eq,        eq,           operator==,   l == r)
+PYBIND11_BINARY_OPERATOR(ne,        ne,           operator!=,   l != r)
+PYBIND11_BINARY_OPERATOR(or,        ror,          operator|,    l | r)
+PYBIND11_BINARY_OPERATOR(gt,        lt,           operator>,    l > r)
+PYBIND11_BINARY_OPERATOR(ge,        le,           operator>=,   l >= r)
+PYBIND11_BINARY_OPERATOR(lt,        gt,           operator<,    l < r)
+PYBIND11_BINARY_OPERATOR(le,        ge,           operator<=,   l <= r)
+//PYBIND11_BINARY_OPERATOR(pow,       rpow,         pow,          std::pow(l,  r))
+PYBIND11_INPLACE_OPERATOR(iadd,     operator+=,   l += r)
+PYBIND11_INPLACE_OPERATOR(isub,     operator-=,   l -= r)
+PYBIND11_INPLACE_OPERATOR(imul,     operator*=,   l *= r)
+PYBIND11_INPLACE_OPERATOR(itruediv, operator/=,   l /= r)
+PYBIND11_INPLACE_OPERATOR(imod,     operator%=,   l %= r)
+PYBIND11_INPLACE_OPERATOR(ilshift,  operator<<=,  l <<= r)
+PYBIND11_INPLACE_OPERATOR(irshift,  operator>>=,  l >>= r)
+PYBIND11_INPLACE_OPERATOR(iand,     operator&=,   l &= r)
+PYBIND11_INPLACE_OPERATOR(ixor,     operator^=,   l ^= r)
+PYBIND11_INPLACE_OPERATOR(ior,      operator|=,   l |= r)
+PYBIND11_UNARY_OPERATOR(neg,        operator-,    -l)
+PYBIND11_UNARY_OPERATOR(pos,        operator+,    +l)
+PYBIND11_UNARY_OPERATOR(abs,        abs,          std::abs(l))
+PYBIND11_UNARY_OPERATOR(hash,       hash,         std::hash<L>()(l))
+PYBIND11_UNARY_OPERATOR(invert,     operator~,    (~l))
+PYBIND11_UNARY_OPERATOR(bool,       operator!,    !!l)
+PYBIND11_UNARY_OPERATOR(int,        int_,         (int) l)
+PYBIND11_UNARY_OPERATOR(float,      float_,       (double) l)
+
+#undef PYBIND11_BINARY_OPERATOR
+#undef PYBIND11_INPLACE_OPERATOR
+#undef PYBIND11_UNARY_OPERATOR
+NAMESPACE_END(detail)
+
+using detail::self;
+
+NAMESPACE_END(PYBIND11_NAMESPACE)
+
+#if defined(_MSC_VER)
+#  pragma warning(pop)
+#endif

dlib/external/pybind11/include/pybind11/options.h

+/*
+    pybind11/options.h: global settings that are configurable at runtime.
+
+    Copyright (c) 2016 Wenzel Jakob <wenzel.jakob@epfl.ch>
+
+    All rights reserved. Use of this source code is governed by a
+    BSD-style license that can be found in the LICENSE file.
+*/
+
+#pragma once
+
+#include "detail/common.h"
+
+NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
+
+class options {
+public:
+
+    // Default RAII constructor, which leaves settings as they currently are.
+    options() : previous_state(global_state()) {}
+
+    // Class is non-copyable.
+    options(const options&) = delete;
+    options& operator=(const options&) = delete;
+
+    // Destructor, which restores settings that were in effect before.
+    ~options() {
+        global_state() = previous_state;
+    }
+
+    // Setter methods (affect the global state):
+
+    options& disable_user_defined_docstrings() & { global_state().show_user_defined_docstrings = false; return *this; }
+
+    options& enable_user_defined_docstrings() & { global_state().show_user_defined_docstrings = true; return *this; }
+
+    options& disable_function_signatures() & { global_state().show_function_signatures = false; return *this; }
+
+    options& enable_function_signatures() & { global_state().show_function_signatures = true; return *this; }
+
+    // Getter methods (return the global state):
+
+    static bool show_user_defined_docstrings() { return global_state().show_user_defined_docstrings; }
+
+    static bool show_function_signatures() { return global_state().show_function_signatures; }
+
+    // This type is not meant to be allocated on the heap.
+    void* operator new(size_t) = delete;
+
+private:
+
+    struct state {
+        bool show_user_defined_docstrings = true;  //< Include user-supplied texts in docstrings.
+        bool show_function_signatures = true;      //< Include auto-generated function signatures in docstrings.
+    };
+
+    static state &global_state() {
+        static state instance;
+        return instance;
+    }
+
+    state previous_state;
+};
+
+NAMESPACE_END(PYBIND11_NAMESPACE)

dlib/external/pybind11/include/pybind11/pybind11.h

+/*
+    pybind11/pybind11.h: Main header file of the C++11 python
+    binding generator library
+
+    Copyright (c) 2016 Wenzel Jakob <wenzel.jakob@epfl.ch>
+
+    All rights reserved. Use of this source code is governed by a
+    BSD-style license that can be found in the LICENSE file.
+*/
+
+#pragma once
+
+#if defined(_MSC_VER)
+#  pragma warning(push)
+#  pragma warning(disable: 4100) // warning C4100: Unreferenced formal parameter
+#  pragma warning(disable: 4127) // warning C4127: Conditional expression is constant
+#  pragma warning(disable: 4512) // warning C4512: Assignment operator was implicitly defined as deleted
+#  pragma warning(disable: 4800) // warning C4800: 'int': forcing value to bool 'true' or 'false' (performance warning)
+#  pragma warning(disable: 4996) // warning C4996: The POSIX name for this item is deprecated. Instead, use the ISO C and C++ conformant name
+#  pragma warning(disable: 4702) // warning C4702: unreachable code
+#  pragma warning(disable: 4522) // warning C4522: multiple assignment operators specified
+#elif defined(__INTEL_COMPILER)
+#  pragma warning(push)
+#  pragma warning(disable: 68)    // integer conversion resulted in a change of sign
+#  pragma warning(disable: 186)   // pointless comparison of unsigned integer with zero
+#  pragma warning(disable: 878)   // incompatible exception specifications
+#  pragma warning(disable: 1334)  // the "template" keyword used for syntactic disambiguation may only be used within a template
+#  pragma warning(disable: 1682)  // implicit conversion of a 64-bit integral type to a smaller integral type (potential portability problem)
+#  pragma warning(disable: 1875)  // offsetof applied to non-POD (Plain Old Data) types is nonstandard
+#  pragma warning(disable: 2196)  // warning #2196: routine is both "inline" and "noinline"
+#elif defined(__GNUG__) && !defined(__clang__)
+#  pragma GCC diagnostic push
+#  pragma GCC diagnostic ignored "-Wunused-but-set-parameter"
+#  pragma GCC diagnostic ignored "-Wunused-but-set-variable"
+#  pragma GCC diagnostic ignored "-Wmissing-field-initializers"
+#  pragma GCC diagnostic ignored "-Wstrict-aliasing"
+#  pragma GCC diagnostic ignored "-Wattributes"
+#  if __GNUC__ >= 7
+#    pragma GCC diagnostic ignored "-Wnoexcept-type"
+#  endif
+#endif
+
+#include "attr.h"
+#include "options.h"
+#include "detail/class.h"
+#include "detail/init.h"
+
+NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
+
+/// Wraps an arbitrary C++ function/method/lambda function/.. into a callable Python object
+class cpp_function : public function {
+public:
+    cpp_function() { }
+    cpp_function(std::nullptr_t) { }
+
+    /// Construct a cpp_function from a vanilla function pointer
+    template <typename Return, typename... Args, typename... Extra>
+    cpp_function(Return (*f)(Args...), const Extra&... extra) {
+        initialize(f, f, extra...);
+    }
+
+    /// Construct a cpp_function from a lambda function (possibly with internal state)
+    template <typename Func, typename... Extra,
+              typename = detail::enable_if_t<detail::is_lambda<Func>::value>>
+    cpp_function(Func &&f, const Extra&... extra) {
+        initialize(std::forward<Func>(f),
+                   (detail::function_signature_t<Func> *) nullptr, extra...);
+    }
+
+    /// Construct a cpp_function from a class method (non-const)
+    template <typename Return, typename Class, typename... Arg, typename... Extra>
+    cpp_function(Return (Class::*f)(Arg...), const Extra&... extra) {
+        initialize([f](Class *c, Arg... args) -> Return { return (c->*f)(args...); },
+                   (Return (*) (Class *, Arg...)) nullptr, extra...);
+    }
+
+    /// Construct a cpp_function from a class method (const)
+    template <typename Return, typename Class, typename... Arg, typename... Extra>
+    cpp_function(Return (Class::*f)(Arg...) const, const Extra&... extra) {
+        initialize([f](const Class *c, Arg... args) -> Return { return (c->*f)(args...); },
+                   (Return (*)(const Class *, Arg ...)) nullptr, extra...);
+    }
+
+    /// Return the function name
+    object name() const { return attr("__name__"); }
+
+protected:
+    /// Space optimization: don't inline this frequently instantiated fragment
+    PYBIND11_NOINLINE detail::function_record *make_function_record() {
+        return new detail::function_record();
+    }
+
+    /// Special internal constructor for functors, lambda functions, etc.
+    template <typename Func, typename Return, typename... Args, typename... Extra>
+    void initialize(Func &&f, Return (*)(Args...), const Extra&... extra) {
+        using namespace detail;
+        struct capture { detail::remove_reference_t<Func> f; };
+
+        /* Store the function including any extra state it might have (e.g. a lambda capture object) */
+        auto rec = make_function_record();
+
+        /* Store the capture object directly in the function record if there is enough space */
+        if (sizeof(capture) <= sizeof(rec->data)) {
+            /* Without these pragmas, GCC warns that there might not be
+               enough space to use the placement new operator. However, the
+               'if' statement above ensures that this is the case. */
+#if defined(__GNUG__) && !defined(__clang__) && __GNUC__ >= 6
+#  pragma GCC diagnostic push
+#  pragma GCC diagnostic ignored "-Wplacement-new"
+#endif
+            new ((capture *) &rec->data) capture { std::forward<Func>(f) };
+#if defined(__GNUG__) && !defined(__clang__) && __GNUC__ >= 6
+#  pragma GCC diagnostic pop
+#endif
+            if (!std::is_trivially_destructible<Func>::value)
+                rec->free_data = [](detail::function_record *r) { ((capture *) &r->data)->~capture(); };
+        } else {
+            rec->data[0] = new capture { std::forward<Func>(f) };
+            rec->free_data = [](detail::function_record *r) { delete ((capture *) r->data[0]); };
+        }
+
+        /* Type casters for the function arguments and return value */
+        using cast_in = detail::argument_loader<Args...>;
+        using cast_out = detail::make_caster<
+            detail::conditional_t<std::is_void<Return>::value, detail::void_type, Return>
+        >;
+
+        static_assert(detail::expected_num_args<Extra...>(sizeof...(Args), cast_in::has_args, cast_in::has_kwargs),
+                      "The number of argument annotations does not match the number of function arguments");
+
+        /* Dispatch code which converts function arguments and performs the actual function call */
+        rec->impl = [](detail::function_call &call) -> handle {
+            cast_in args_converter;
+
+            /* Try to cast the function arguments into the C++ domain */
+            if (!args_converter.load_args(call))
+                return PYBIND11_TRY_NEXT_OVERLOAD;
+
+            /* Invoke call policy pre-call hook */
+            detail::process_attributes<Extra...>::precall(call);
+
+            /* Get a pointer to the capture object */
+            auto data = (sizeof(capture) <= sizeof(call.func.data)
+                         ? &call.func.data : call.func.data[0]);
+            capture *cap = const_cast<capture *>(reinterpret_cast<const capture *>(data));
+
+            /* Override policy for rvalues -- usually to enforce rvp::move on an rvalue */
+            const auto policy = detail::return_value_policy_override<Return>::policy(call.func.policy);
+
+            /* Function scope guard -- defaults to the compile-to-nothing `void_type` */
+            using Guard = detail::extract_guard_t<Extra...>;
+
+            /* Perform the function call */
+            handle result = cast_out::cast(
+                std::move(args_converter).template call<Return, Guard>(cap->f), policy, call.parent);
+
+            /* Invoke call policy post-call hook */
+            detail::process_attributes<Extra...>::postcall(call, result);
+
+            return result;
+        };
+
+        /* Process any user-provided function attributes */
+        detail::process_attributes<Extra...>::init(extra..., rec);
+
+        /* Generate a readable signature describing the function's arguments and return value types */
+        static constexpr auto signature = _("(") + cast_in::arg_names + _(") -> ") + cast_out::name;
+        PYBIND11_DESCR_CONSTEXPR auto types = decltype(signature)::types();
+
+        /* Register the function with Python from generic (non-templated) code */
+        initialize_generic(rec, signature.text, types.data(), sizeof...(Args));
+
+        if (cast_in::has_args) rec->has_args = true;
+        if (cast_in::has_kwargs) rec->has_kwargs = true;
+
+        /* Stash some additional information used by an important optimization in 'functional.h' */
+        using FunctionType = Return (*)(Args...);
+        constexpr bool is_function_ptr =
+            std::is_convertible<Func, FunctionType>::value &&
+            sizeof(capture) == sizeof(void *);
+        if (is_function_ptr) {
+            rec->is_stateless = true;
+            rec->data[1] = const_cast<void *>(reinterpret_cast<const void *>(&typeid(FunctionType)));
+        }
+    }
+
+    /// Register a function call with Python (generic non-templated code goes here)
+    void initialize_generic(detail::function_record *rec, const char *text,
+                            const std::type_info *const *types, size_t args) {
+
+        /* Create copies of all referenced C-style strings */
+        rec->name = strdup(rec->name ? rec->name : "");
+        if (rec->doc) rec->doc = strdup(rec->doc);
+        for (auto &a: rec->args) {
+            if (a.name)
+                a.name = strdup(a.name);
+            if (a.descr)
+                a.descr = strdup(a.descr);
+            else if (a.value)
+                a.descr = strdup(a.value.attr("__repr__")().cast<std::string>().c_str());
+        }
+
+        rec->is_constructor = !strcmp(rec->name, "__init__") || !strcmp(rec->name, "__setstate__");
+
+#if !defined(NDEBUG) && !defined(PYBIND11_DISABLE_NEW_STYLE_INIT_WARNING)
+        if (rec->is_constructor && !rec->is_new_style_constructor) {
+            const auto class_name = std::string(((PyTypeObject *) rec->scope.ptr())->tp_name);
+            const auto func_name = std::string(rec->name);
+            PyErr_WarnEx(
+                PyExc_FutureWarning,
+                ("pybind11-bound class '" + class_name + "' is using an old-style "
+                 "placement-new '" + func_name + "' which has been deprecated. See "
+                 "the upgrade guide in pybind11's docs. This message is only visible "
+                 "when compiled in debug mode.").c_str(), 0
+            );
+        }
+#endif
+
+        /* Generate a proper function signature */
+        std::string signature;
+        size_t type_index = 0, arg_index = 0;
+        for (auto *pc = text; *pc != '\0'; ++pc) {
+            const auto c = *pc;
+
+            if (c == '{') {
+                // Write arg name for everything except *args and **kwargs.
+                if (*(pc + 1) == '*')
+                    continue;
+
+                if (arg_index < rec->args.size() && rec->args[arg_index].name) {
+                    signature += rec->args[arg_index].name;
+                } else if (arg_index == 0 && rec->is_method) {
+                    signature += "self";
+                } else {
+                    signature += "arg" + std::to_string(arg_index - (rec->is_method ? 1 : 0));
+                }
+                signature += ": ";
+            } else if (c == '}') {
+                // Write default value if available.
+                if (arg_index < rec->args.size() && rec->args[arg_index].descr) {
+                    signature += "=";
+                    signature += rec->args[arg_index].descr;
+                }
+                arg_index++;
+            } else if (c == '%') {
+                const std::type_info *t = types[type_index++];
+                if (!t)
+                    pybind11_fail("Internal error while parsing type signature (1)");
+                if (auto tinfo = detail::get_type_info(*t)) {
+                    handle th((PyObject *) tinfo->type);
+                    signature +=
+                        th.attr("__module__").cast<std::string>() + "." +
+                        th.attr("__qualname__").cast<std::string>(); // Python 3.3+, but we backport it to earlier versions
+                } else if (rec->is_new_style_constructor && arg_index == 0) {
+                    // A new-style `__init__` takes `self` as `value_and_holder`.
+                    // Rewrite it to the proper class type.
+                    signature +=
+                        rec->scope.attr("__module__").cast<std::string>() + "." +
+                        rec->scope.attr("__qualname__").cast<std::string>();
+                } else {
+                    std::string tname(t->name());
+                    detail::clean_type_id(tname);
+                    signature += tname;
+                }
+            } else {
+                signature += c;
+            }
+        }
+        if (arg_index != args || types[type_index] != nullptr)
+            pybind11_fail("Internal error while parsing type signature (2)");
+
+#if PY_MAJOR_VERSION < 3
+        if (strcmp(rec->name, "__next__") == 0) {
+            std::free(rec->name);
+            rec->name = strdup("next");
+        } else if (strcmp(rec->name, "__bool__") == 0) {
+            std::free(rec->name);
+            rec->name = strdup("__nonzero__");
+        }
+#endif
+        rec->signature = strdup(signature.c_str());
+        rec->args.shrink_to_fit();
+        rec->nargs = (std::uint16_t) args;
+
+        if (rec->sibling && PYBIND11_INSTANCE_METHOD_CHECK(rec->sibling.ptr()))
+            rec->sibling = PYBIND11_INSTANCE_METHOD_GET_FUNCTION(rec->sibling.ptr());
+
+        detail::function_record *chain = nullptr, *chain_start = rec;
+        if (rec->sibling) {
+            if (PyCFunction_Check(rec->sibling.ptr())) {
+                auto rec_capsule = reinterpret_borrow<capsule>(PyCFunction_GET_SELF(rec->sibling.ptr()));
+                chain = (detail::function_record *) rec_capsule;
+                /* Never append a method to an overload chain of a parent class;
+                   instead, hide the parent's overloads in this case */
+                if (!chain->scope.is(rec->scope))
+                    chain = nullptr;
+            }
+            // Don't trigger for things like the default __init__, which are wrapper_descriptors that we are intentionally replacing
+            else if (!rec->sibling.is_none() && rec->name[0] != '_')
+                pybind11_fail("Cannot overload existing non-function object \"" + std::string(rec->name) +
+                        "\" with a function of the same name");
+        }
+
+        if (!chain) {
+            /* No existing overload was found, create a new function object */
+            rec->def = new PyMethodDef();
+            std::memset(rec->def, 0, sizeof(PyMethodDef));
+            rec->def->ml_name = rec->name;
+            rec->def->ml_meth = reinterpret_cast<PyCFunction>(*dispatcher);
+            rec->def->ml_flags = METH_VARARGS | METH_KEYWORDS;
+
+            capsule rec_capsule(rec, [](void *ptr) {
+                destruct((detail::function_record *) ptr);
+            });
+
+            object scope_module;
+            if (rec->scope) {
+                if (hasattr(rec->scope, "__module__")) {
+                    scope_module = rec->scope.attr("__module__");
+                } else if (hasattr(rec->scope, "__name__")) {
+                    scope_module = rec->scope.attr("__name__");
+                }
+            }
+
+            m_ptr = PyCFunction_NewEx(rec->def, rec_capsule.ptr(), scope_module.ptr());
+            if (!m_ptr)
+                pybind11_fail("cpp_function::cpp_function(): Could not allocate function object");
+        } else {
+            /* Append at the end of the overload chain */
+            m_ptr = rec->sibling.ptr();
+            inc_ref();
+            chain_start = chain;
+            if (chain->is_method != rec->is_method)
+                pybind11_fail("overloading a method with both static and instance methods is not supported; "
+                    #if defined(NDEBUG)
+                        "compile in debug mode for more details"
+                    #else
+                        "error while attempting to bind " + std::string(rec->is_method ? "instance" : "static") + " method " +
+                        std::string(pybind11::str(rec->scope.attr("__name__"))) + "." + std::string(rec->name) + signature
+                    #endif
+                );
+            while (chain->next)
+                chain = chain->next;
+            chain->next = rec;
+        }
+
+        std::string signatures;
+        int index = 0;
+        /* Create a nice pydoc rec including all signatures and
+           docstrings of the functions in the overload chain */
+        if (chain && options::show_function_signatures()) {
+            // First a generic signature
+            signatures += rec->name;
+            signatures += "(*args, **kwargs)\n";
+            signatures += "Overloaded function.\n\n";
+        }
+        // Then specific overload signatures
+        bool first_user_def = true;
+        for (auto it = chain_start; it != nullptr; it = it->next) {
+            if (options::show_function_signatures()) {
+                if (index > 0) signatures += "\n";
+                if (chain)
+                    signatures += std::to_string(++index) + ". ";
+                signatures += rec->name;
+                signatures += it->signature;
+                signatures += "\n";
+            }
+            if (it->doc && strlen(it->doc) > 0 && options::show_user_defined_docstrings()) {
+                // If we're appending another docstring, and aren't printing function signatures, we
+                // need to append a newline first:
+                if (!options::show_function_signatures()) {
+                    if (first_user_def) first_user_def = false;
+                    else signatures += "\n";
+                }
+                if (options::show_function_signatures()) signatures += "\n";
+                signatures += it->doc;
+                if (options::show_function_signatures()) signatures += "\n";
+            }
+        }
+
+        /* Install docstring */
+        PyCFunctionObject *func = (PyCFunctionObject *) m_ptr;
+        if (func->m_ml->ml_doc)
+            std::free(const_cast<char *>(func->m_ml->ml_doc));
+        func->m_ml->ml_doc = strdup(signatures.c_str());
+
+        if (rec->is_method) {
+            m_ptr = PYBIND11_INSTANCE_METHOD_NEW(m_ptr, rec->scope.ptr());
+            if (!m_ptr)
+                pybind11_fail("cpp_function::cpp_function(): Could not allocate instance method object");
+            Py_DECREF(func);
+        }
+    }
+
+    /// When a cpp_function is GCed, release any memory allocated by pybind11
+    static void destruct(detail::function_record *rec) {
+        while (rec) {
+            detail::function_record *next = rec->next;
+            if (rec->free_data)
+                rec->free_data(rec);
+            std::free((char *) rec->name);
+            std::free((char *) rec->doc);
+            std::free((char *) rec->signature);
+            for (auto &arg: rec->args) {
+                std::free(const_cast<char *>(arg.name));
+                std::free(const_cast<char *>(arg.descr));
+                arg.value.dec_ref();
+            }
+            if (rec->def) {
+                std::free(const_cast<char *>(rec->def->ml_doc));
+                delete rec->def;
+            }
+            delete rec;
+            rec = next;
+        }
+    }
+
+    /// Main dispatch logic for calls to functions bound using pybind11
+    static PyObject *dispatcher(PyObject *self, PyObject *args_in, PyObject *kwargs_in) {
+        using namespace detail;
+
+        /* Iterator over the list of potentially admissible overloads */
+        function_record *overloads = (function_record *) PyCapsule_GetPointer(self, nullptr),
+                        *it = overloads;
+
+        /* Need to know how many arguments + keyword arguments there are to pick the right overload */
+        const size_t n_args_in = (size_t) PyTuple_GET_SIZE(args_in);
+
+        handle parent = n_args_in > 0 ? PyTuple_GET_ITEM(args_in, 0) : nullptr,
+               result = PYBIND11_TRY_NEXT_OVERLOAD;
+
+        auto self_value_and_holder = value_and_holder();
+        if (overloads->is_constructor) {
+            const auto tinfo = get_type_info((PyTypeObject *) overloads->scope.ptr());
+            const auto pi = reinterpret_cast<instance *>(parent.ptr());
+            self_value_and_holder = pi->get_value_and_holder(tinfo, false);
+
+            if (!self_value_and_holder.type || !self_value_and_holder.inst) {
+                PyErr_SetString(PyExc_TypeError, "__init__(self, ...) called with invalid `self` argument");
+                return nullptr;
+            }
+
+            // If this value is already registered it must mean __init__ is invoked multiple times;
+            // we really can't support that in C++, so just ignore the second __init__.
+            if (self_value_and_holder.instance_registered())
+                return none().release().ptr();
+        }
+
+        try {
+            // We do this in two passes: in the first pass, we load arguments with `convert=false`;
+            // in the second, we allow conversion (except for arguments with an explicit
+            // py::arg().noconvert()).  This lets us prefer calls without conversion, with
+            // conversion as a fallback.
+            std::vector<function_call> second_pass;
+
+            // However, if there are no overloads, we can just skip the no-convert pass entirely
+            const bool overloaded = it != nullptr && it->next != nullptr;
+
+            for (; it != nullptr; it = it->next) {
+
+                /* For each overload:
+                   1. Copy all positional arguments we were given, also checking to make sure that
+                      named positional arguments weren't *also* specified via kwarg.
+                   2. If we weren't given enough, try to make up the omitted ones by checking
+                      whether they were provided by a kwarg matching the `py::arg("name")` name.  If
+                      so, use it (and remove it from kwargs; if not, see if the function binding
+                      provided a default that we can use.
+                   3. Ensure that either all keyword arguments were "consumed", or that the function
+                      takes a kwargs argument to accept unconsumed kwargs.
+                   4. Any positional arguments still left get put into a tuple (for args), and any
+                      leftover kwargs get put into a dict.
+                   5. Pack everything into a vector; if we have py::args or py::kwargs, they are an
+                      extra tuple or dict at the end of the positional arguments.
+                   6. Call the function call dispatcher (function_record::impl)
+
+                   If one of these fail, move on to the next overload and keep trying until we get a
+                   result other than PYBIND11_TRY_NEXT_OVERLOAD.
+                 */
+
+                function_record &func = *it;
+                size_t pos_args = func.nargs;    // Number of positional arguments that we need
+                if (func.has_args) --pos_args;   // (but don't count py::args
+                if (func.has_kwargs) --pos_args; //  or py::kwargs)
+
+                if (!func.has_args && n_args_in > pos_args)
+                    continue; // Too many arguments for this overload
+
+                if (n_args_in < pos_args && func.args.size() < pos_args)
+                    continue; // Not enough arguments given, and not enough defaults to fill in the blanks
+
+                function_call call(func, parent);
+
+                size_t args_to_copy = std::min(pos_args, n_args_in);
+                size_t args_copied = 0;
+
+                // 0. Inject new-style `self` argument
+                if (func.is_new_style_constructor) {
+                    // The `value` may have been preallocated by an old-style `__init__`
+                    // if it was a preceding candidate for overload resolution.
+                    if (self_value_and_holder)
+                        self_value_and_holder.type->dealloc(self_value_and_holder);
+
+                    call.init_self = PyTuple_GET_ITEM(args_in, 0);
+                    call.args.push_back(reinterpret_cast<PyObject *>(&self_value_and_holder));
+                    call.args_convert.push_back(false);
+                    ++args_copied;
+                }
+
+                // 1. Copy any position arguments given.
+                bool bad_arg = false;
+                for (; args_copied < args_to_copy; ++args_copied) {
+                    argument_record *arg_rec = args_copied < func.args.size() ? &func.args[args_copied] : nullptr;
+                    if (kwargs_in && arg_rec && arg_rec->name && PyDict_GetItemString(kwargs_in, arg_rec->name)) {
+                        bad_arg = true;
+                        break;
+                    }
+
+                    handle arg(PyTuple_GET_ITEM(args_in, args_copied));
+                    if (arg_rec && !arg_rec->none && arg.is_none()) {
+                        bad_arg = true;
+                        break;
+                    }
+                    call.args.push_back(arg);
+                    call.args_convert.push_back(arg_rec ? arg_rec->convert : true);
+                }
+                if (bad_arg)
+                    continue; // Maybe it was meant for another overload (issue #688)
+
+                // We'll need to copy this if we steal some kwargs for defaults
+                dict kwargs = reinterpret_borrow<dict>(kwargs_in);
+
+                // 2. Check kwargs and, failing that, defaults that may help complete the list
+                if (args_copied < pos_args) {
+                    bool copied_kwargs = false;
+
+                    for (; args_copied < pos_args; ++args_copied) {
+                        const auto &arg = func.args[args_copied];
+
+                        handle value;
+                        if (kwargs_in && arg.name)
+                            value = PyDict_GetItemString(kwargs.ptr(), arg.name);
+
+                        if (value) {
+                            // Consume a kwargs value
+                            if (!copied_kwargs) {
+                                kwargs = reinterpret_steal<dict>(PyDict_Copy(kwargs.ptr()));
+                                copied_kwargs = true;
+                            }
+                            PyDict_DelItemString(kwargs.ptr(), arg.name);
+                        } else if (arg.value) {
+                            value = arg.value;
+                        }
+
+                        if (value) {
+                            call.args.push_back(value);
+                            call.args_convert.push_back(arg.convert);
+                        }
+                        else
+                            break;
+                    }
+
+                    if (args_copied < pos_args)
+                        continue; // Not enough arguments, defaults, or kwargs to fill the positional arguments
+                }
+
+                // 3. Check everything was consumed (unless we have a kwargs arg)
+                if (kwargs && kwargs.size() > 0 && !func.has_kwargs)
+                    continue; // Unconsumed kwargs, but no py::kwargs argument to accept them
+
+                // 4a. If we have a py::args argument, create a new tuple with leftovers
+                tuple extra_args;
+                if (func.has_args) {
+                    if (args_to_copy == 0) {
+                        // We didn't copy out any position arguments from the args_in tuple, so we
+                        // can reuse it directly without copying:
+                        extra_args = reinterpret_borrow<tuple>(args_in);
+                    } else if (args_copied >= n_args_in) {
+                        extra_args = tuple(0);
+                    } else {
+                        size_t args_size = n_args_in - args_copied;
+                        extra_args = tuple(args_size);
+                        for (size_t i = 0; i < args_size; ++i) {
+                            handle item = PyTuple_GET_ITEM(args_in, args_copied + i);
+                            extra_args[i] = item.inc_ref().ptr();
+                        }
+                    }
+                    call.args.push_back(extra_args);
+                    call.args_convert.push_back(false);
+                }
+
+                // 4b. If we have a py::kwargs, pass on any remaining kwargs
+                if (func.has_kwargs) {
+                    if (!kwargs.ptr())
+                        kwargs = dict(); // If we didn't get one, send an empty one
+                    call.args.push_back(kwargs);
+                    call.args_convert.push_back(false);
+                }
+
+                // 5. Put everything in a vector.  Not technically step 5, we've been building it
+                // in `call.args` all along.
+                #if !defined(NDEBUG)
+                if (call.args.size() != func.nargs || call.args_convert.size() != func.nargs)
+                    pybind11_fail("Internal error: function call dispatcher inserted wrong number of arguments!");
+                #endif
+
+                std::vector<bool> second_pass_convert;
+                if (overloaded) {
+                    // We're in the first no-convert pass, so swap out the conversion flags for a
+                    // set of all-false flags.  If the call fails, we'll swap the flags back in for
+                    // the conversion-allowed call below.
+                    second_pass_convert.resize(func.nargs, false);
+                    call.args_convert.swap(second_pass_convert);
+                }
+
+                // 6. Call the function.
+                try {
+                    loader_life_support guard{};
+                    result = func.impl(call);
+                } catch (reference_cast_error &) {
+                    result = PYBIND11_TRY_NEXT_OVERLOAD;
+                }
+
+                if (result.ptr() != PYBIND11_TRY_NEXT_OVERLOAD)
+                    break;
+
+                if (overloaded) {
+                    // The (overloaded) call failed; if the call has at least one argument that
+                    // permits conversion (i.e. it hasn't been explicitly specified `.noconvert()`)
+                    // then add this call to the list of second pass overloads to try.
+                    for (size_t i = func.is_method ? 1 : 0; i < pos_args; i++) {
+                        if (second_pass_convert[i]) {
+                            // Found one: swap the converting flags back in and store the call for
+                            // the second pass.
+                            call.args_convert.swap(second_pass_convert);
+                            second_pass.push_back(std::move(call));
+                            break;
+                        }
+                    }
+                }
+            }
+
+            if (overloaded && !second_pass.empty() && result.ptr() == PYBIND11_TRY_NEXT_OVERLOAD) {
+                // The no-conversion pass finished without success, try again with conversion allowed
+                for (auto &call : second_pass) {
+                    try {
+                        loader_life_support guard{};
+                        result = call.func.impl(call);
+                    } catch (reference_cast_error &) {
+                        result = PYBIND11_TRY_NEXT_OVERLOAD;
+                    }
+
+                    if (result.ptr() != PYBIND11_TRY_NEXT_OVERLOAD)
+                        break;
+                }
+            }
+        } catch (error_already_set &e) {
+            e.restore();
+            return nullptr;
+        } catch (...) {
+            /* When an exception is caught, give each registered exception
+               translator a chance to translate it to a Python exception
+               in reverse order of registration.
+
+               A translator may choose to do one of the following:
+
+                - catch the exception and call PyErr_SetString or PyErr_SetObject
+                  to set a standard (or custom) Python exception, or
+                - do nothing and let the exception fall through to the next translator, or
+                - delegate translation to the next translator by throwing a new type of exception. */
+
+            auto last_exception = std::current_exception();
+            auto &registered_exception_translators = get_internals().registered_exception_translators;
+            for (auto& translator : registered_exception_translators) {
+                try {
+                    translator(last_exception);
+                } catch (...) {
+                    last_exception = std::current_exception();
+                    continue;
+                }
+                return nullptr;
+            }
+            PyErr_SetString(PyExc_SystemError, "Exception escaped from default exception translator!");
+            return nullptr;
+        }
+
+        auto append_note_if_missing_header_is_suspected = [](std::string &msg) {
+            if (msg.find("std::") != std::string::npos) {
+                msg += "\n\n"
+                       "Did you forget to `#include <pybind11/stl.h>`? Or <pybind11/complex.h>,\n"
+                       "<pybind11/functional.h>, <pybind11/chrono.h>, etc. Some automatic\n"
+                       "conversions are optional and require extra headers to be included\n"
+                       "when compiling your pybind11 module.";
+            }
+        };
+
+        if (result.ptr() == PYBIND11_TRY_NEXT_OVERLOAD) {
+            if (overloads->is_operator)
+                return handle(Py_NotImplemented).inc_ref().ptr();
+
+            std::string msg = std::string(overloads->name) + "(): incompatible " +
+                std::string(overloads->is_constructor ? "constructor" : "function") +
+                " arguments. The following argument types are supported:\n";
+
+            int ctr = 0;
+            for (function_record *it2 = overloads; it2 != nullptr; it2 = it2->next) {
+                msg += "    "+ std::to_string(++ctr) + ". ";
+
+                bool wrote_sig = false;
+                if (overloads->is_constructor) {
+                    // For a constructor, rewrite `(self: Object, arg0, ...) -> NoneType` as `Object(arg0, ...)`
+                    std::string sig = it2->signature;
+                    size_t start = sig.find('(') + 7; // skip "(self: "
+                    if (start < sig.size()) {
+                        // End at the , for the next argument
+                        size_t end = sig.find(", "), next = end + 2;
+                        size_t ret = sig.rfind(" -> ");
+                        // Or the ), if there is no comma:
+                        if (end >= sig.size()) next = end = sig.find(')');
+                        if (start < end && next < sig.size()) {
+                            msg.append(sig, start, end - start);
+                            msg += '(';
+                            msg.append(sig, next, ret - next);
+                            wrote_sig = true;
+                        }
+                    }
+                }
+                if (!wrote_sig) msg += it2->signature;
+
+                msg += "\n";
+            }
+            msg += "\nInvoked with: ";
+            auto args_ = reinterpret_borrow<tuple>(args_in);
+            bool some_args = false;
+            for (size_t ti = overloads->is_constructor ? 1 : 0; ti < args_.size(); ++ti) {
+                if (!some_args) some_args = true;
+                else msg += ", ";
+                msg += pybind11::repr(args_[ti]);
+            }
+            if (kwargs_in) {
+                auto kwargs = reinterpret_borrow<dict>(kwargs_in);
+                if (kwargs.size() > 0) {
+                    if (some_args) msg += "; ";
+                    msg += "kwargs: ";
+                    bool first = true;
+                    for (auto kwarg : kwargs) {
+                        if (first) first = false;
+                        else msg += ", ";
+                        msg += pybind11::str("{}={!r}").format(kwarg.first, kwarg.second);
+                    }
+                }
+            }
+
+            append_note_if_missing_header_is_suspected(msg);
+            PyErr_SetString(PyExc_TypeError, msg.c_str());
+            return nullptr;
+        } else if (!result) {
+            std::string msg = "Unable to convert function return value to a "
+                              "Python type! The signature was\n\t";
+            msg += it->signature;
+            append_note_if_missing_header_is_suspected(msg);
+            PyErr_SetString(PyExc_TypeError, msg.c_str());
+            return nullptr;
+        } else {
+            if (overloads->is_constructor && !self_value_and_holder.holder_constructed()) {
+                auto *pi = reinterpret_cast<instance *>(parent.ptr());
+                self_value_and_holder.type->init_instance(pi, nullptr);
+            }
+            return result.ptr();
+        }
+    }
+};
+
+/// Wrapper for Python extension modules
+class module : public object {
+public:
+    PYBIND11_OBJECT_DEFAULT(module, object, PyModule_Check)
+
+    /// Create a new top-level Python module with the given name and docstring
+    explicit module(const char *name, const char *doc = nullptr) {
+        if (!options::show_user_defined_docstrings()) doc = nullptr;
+#if PY_MAJOR_VERSION >= 3
+        PyModuleDef *def = new PyModuleDef();
+        std::memset(def, 0, sizeof(PyModuleDef));
+        def->m_name = name;
+        def->m_doc = doc;
+        def->m_size = -1;
+        Py_INCREF(def);
+        m_ptr = PyModule_Create(def);
+#else
+        m_ptr = Py_InitModule3(name, nullptr, doc);
+#endif
+        if (m_ptr == nullptr)
+            pybind11_fail("Internal error in module::module()");
+        inc_ref();
+    }
+
+    /** \rst
+        Create Python binding for a new function within the module scope. ``Func``
+        can be a plain C++ function, a function pointer, or a lambda function. For
+        details on the ``Extra&& ... extra`` argument, see section :ref:`extras`.
+    \endrst */
+    template <typename Func, typename... Extra>
+    module &def(const char *name_, Func &&f, const Extra& ... extra) {
+        cpp_function func(std::forward<Func>(f), name(name_), scope(*this),
+                          sibling(getattr(*this, name_, none())), extra...);
+        // NB: allow overwriting here because cpp_function sets up a chain with the intention of
+        // overwriting (and has already checked internally that it isn't overwriting non-functions).
+        add_object(name_, func, true /* overwrite */);
+        return *this;
+    }
+
+    /** \rst
+        Create and return a new Python submodule with the given name and docstring.
+        This also works recursively, i.e.
+
+        .. code-block:: cpp
+
+            py::module m("example", "pybind11 example plugin");
+            py::module m2 = m.def_submodule("sub", "A submodule of 'example'");
+            py::module m3 = m2.def_submodule("subsub", "A submodule of 'example.sub'");
+    \endrst */
+    module def_submodule(const char *name, const char *doc = nullptr) {
+        std::string full_name = std::string(PyModule_GetName(m_ptr))
+            + std::string(".") + std::string(name);
+        auto result = reinterpret_borrow<module>(PyImport_AddModule(full_name.c_str()));
+        if (doc && options::show_user_defined_docstrings())
+            result.attr("__doc__") = pybind11::str(doc);
+        attr(name) = result;
+        return result;
+    }
+
+    /// Import and return a module or throws `error_already_set`.
+    static module import(const char *name) {
+        PyObject *obj = PyImport_ImportModule(name);
+        if (!obj)
+            throw error_already_set();
+        return reinterpret_steal<module>(obj);
+    }
+
+    /// Reload the module or throws `error_already_set`.
+    void reload() {
+        PyObject *obj = PyImport_ReloadModule(ptr());
+        if (!obj)
+            throw error_already_set();
+        *this = reinterpret_steal<module>(obj);
+    }
+
+    // Adds an object to the module using the given name.  Throws if an object with the given name
+    // already exists.
+    //
+    // overwrite should almost always be false: attempting to overwrite objects that pybind11 has
+    // established will, in most cases, break things.
+    PYBIND11_NOINLINE void add_object(const char *name, handle obj, bool overwrite = false) {
+        if (!overwrite && hasattr(*this, name))
+            pybind11_fail("Error during initialization: multiple incompatible definitions with name \"" +
+                    std::string(name) + "\"");
+
+        PyModule_AddObject(ptr(), name, obj.inc_ref().ptr() /* steals a reference */);
+    }
+};
+
+/// \ingroup python_builtins
+/// Return a dictionary representing the global variables in the current execution frame,
+/// or ``__main__.__dict__`` if there is no frame (usually when the interpreter is embedded).
+inline dict globals() {
+    PyObject *p = PyEval_GetGlobals();
+    return reinterpret_borrow<dict>(p ? p : module::import("__main__").attr("__dict__").ptr());
+}
+
+NAMESPACE_BEGIN(detail)
+/// Generic support for creating new Python heap types
+class generic_type : public object {
+    template <typename...> friend class class_;
+public:
+    PYBIND11_OBJECT_DEFAULT(generic_type, object, PyType_Check)
+protected:
+    void initialize(const type_record &rec) {
+        if (rec.scope && hasattr(rec.scope, rec.name))
+            pybind11_fail("generic_type: cannot initialize type \"" + std::string(rec.name) +
+                          "\": an object with that name is already defined");
+
+        if (rec.module_local ? get_local_type_info(*rec.type) : get_global_type_info(*rec.type))
+            pybind11_fail("generic_type: type \"" + std::string(rec.name) +
+                          "\" is already registered!");
+
+        m_ptr = make_new_python_type(rec);
+
+        /* Register supplemental type information in C++ dict */
+        auto *tinfo = new detail::type_info();
+        tinfo->type = (PyTypeObject *) m_ptr;
+        tinfo->cpptype = rec.type;
+        tinfo->type_size = rec.type_size;
+        tinfo->operator_new = rec.operator_new;
+        tinfo->holder_size_in_ptrs = size_in_ptrs(rec.holder_size);
+        tinfo->init_instance = rec.init_instance;
+        tinfo->dealloc = rec.dealloc;
+        tinfo->simple_type = true;
+        tinfo->simple_ancestors = true;
+        tinfo->default_holder = rec.default_holder;
+        tinfo->module_local = rec.module_local;
+
+        auto &internals = get_internals();
+        auto tindex = std::type_index(*rec.type);
+        tinfo->direct_conversions = &internals.direct_conversions[tindex];
+        if (rec.module_local)
+            registered_local_types_cpp()[tindex] = tinfo;
+        else
+            internals.registered_types_cpp[tindex] = tinfo;
+        internals.registered_types_py[(PyTypeObject *) m_ptr] = { tinfo };
+
+        if (rec.bases.size() > 1 || rec.multiple_inheritance) {
+            mark_parents_nonsimple(tinfo->type);
+            tinfo->simple_ancestors = false;
+        }
+        else if (rec.bases.size() == 1) {
+            auto parent_tinfo = get_type_info((PyTypeObject *) rec.bases[0].ptr());
+            tinfo->simple_ancestors = parent_tinfo->simple_ancestors;
+        }
+
+        if (rec.module_local) {
+            // Stash the local typeinfo and loader so that external modules can access it.
+            tinfo->module_local_load = &type_caster_generic::local_load;
+            setattr(m_ptr, PYBIND11_MODULE_LOCAL_ID, capsule(tinfo));
+        }
+    }
+
+    /// Helper function which tags all parents of a type using mult. inheritance
+    void mark_parents_nonsimple(PyTypeObject *value) {
+        auto t = reinterpret_borrow<tuple>(value->tp_bases);
+        for (handle h : t) {
+            auto tinfo2 = get_type_info((PyTypeObject *) h.ptr());
+            if (tinfo2)
+                tinfo2->simple_type = false;
+            mark_parents_nonsimple((PyTypeObject *) h.ptr());
+        }
+    }
+
+    void install_buffer_funcs(
+            buffer_info *(*get_buffer)(PyObject *, void *),
+            void *get_buffer_data) {
+        PyHeapTypeObject *type = (PyHeapTypeObject*) m_ptr;
+        auto tinfo = detail::get_type_info(&type->ht_type);
+
+        if (!type->ht_type.tp_as_buffer)
+            pybind11_fail(
+                "To be able to register buffer protocol support for the type '" +
+                std::string(tinfo->type->tp_name) +
+                "' the associated class<>(..) invocation must "
+                "include the pybind11::buffer_protocol() annotation!");
+
+        tinfo->get_buffer = get_buffer;
+        tinfo->get_buffer_data = get_buffer_data;
+    }
+
+    // rec_func must be set for either fget or fset.
+    void def_property_static_impl(const char *name,
+                                  handle fget, handle fset,
+                                  detail::function_record *rec_func) {
+        const auto is_static = rec_func && !(rec_func->is_method && rec_func->scope);
+        const auto has_doc = rec_func && rec_func->doc && pybind11::options::show_user_defined_docstrings();
+        auto property = handle((PyObject *) (is_static ? get_internals().static_property_type
+                                                       : &PyProperty_Type));
+        attr(name) = property(fget.ptr() ? fget : none(),
+                              fset.ptr() ? fset : none(),
+                              /*deleter*/none(),
+                              pybind11::str(has_doc ? rec_func->doc : ""));
+    }
+};
+
+/// Set the pointer to operator new if it exists. The cast is needed because it can be overloaded.
+template <typename T, typename = void_t<decltype(static_cast<void *(*)(size_t)>(T::operator new))>>
+void set_operator_new(type_record *r) { r->operator_new = &T::operator new; }
+
+template <typename> void set_operator_new(...) { }
+
+template <typename T, typename SFINAE = void> struct has_operator_delete : std::false_type { };
+template <typename T> struct has_operator_delete<T, void_t<decltype(static_cast<void (*)(void *)>(T::operator delete))>>
+    : std::true_type { };
+template <typename T, typename SFINAE = void> struct has_operator_delete_size : std::false_type { };
+template <typename T> struct has_operator_delete_size<T, void_t<decltype(static_cast<void (*)(void *, size_t)>(T::operator delete))>>
+    : std::true_type { };
+/// Call class-specific delete if it exists or global otherwise. Can also be an overload set.
+template <typename T, enable_if_t<has_operator_delete<T>::value, int> = 0>
+void call_operator_delete(T *p, size_t) { T::operator delete(p); }
+template <typename T, enable_if_t<!has_operator_delete<T>::value && has_operator_delete_size<T>::value, int> = 0>
+void call_operator_delete(T *p, size_t s) { T::operator delete(p, s); }
+
+inline void call_operator_delete(void *p, size_t) { ::operator delete(p); }
+
+NAMESPACE_END(detail)
+
+/// Given a pointer to a member function, cast it to its `Derived` version.
+/// Forward everything else unchanged.
+template <typename /*Derived*/, typename F>
+auto method_adaptor(F &&f) -> decltype(std::forward<F>(f)) { return std::forward<F>(f); }
+
+template <typename Derived, typename Return, typename Class, typename... Args>
+auto method_adaptor(Return (Class::*pmf)(Args...)) -> Return (Derived::*)(Args...) {
+    static_assert(detail::is_accessible_base_of<Class, Derived>::value,
+        "Cannot bind an inaccessible base class method; use a lambda definition instead");
+    return pmf;
+}
+
+template <typename Derived, typename Return, typename Class, typename... Args>
+auto method_adaptor(Return (Class::*pmf)(Args...) const) -> Return (Derived::*)(Args...) const {
+    static_assert(detail::is_accessible_base_of<Class, Derived>::value,
+        "Cannot bind an inaccessible base class method; use a lambda definition instead");
+    return pmf;
+}
+
+template <typename type_, typename... options>
+class class_ : public detail::generic_type {
+    template <typename T> using is_holder = detail::is_holder_type<type_, T>;
+    template <typename T> using is_subtype = detail::is_strict_base_of<type_, T>;
+    template <typename T> using is_base = detail::is_strict_base_of<T, type_>;
+    // struct instead of using here to help MSVC:
+    template <typename T> struct is_valid_class_option :
+        detail::any_of<is_holder<T>, is_subtype<T>, is_base<T>> {};
+
+public:
+    using type = type_;
+    using type_alias = detail::exactly_one_t<is_subtype, void, options...>;
+    constexpr static bool has_alias = !std::is_void<type_alias>::value;
+    using holder_type = detail::exactly_one_t<is_holder, std::unique_ptr<type>, options...>;
+
+    static_assert(detail::all_of<is_valid_class_option<options>...>::value,
+            "Unknown/invalid class_ template parameters provided");
+
+    static_assert(!has_alias || std::is_polymorphic<type>::value,
+            "Cannot use an alias class with a non-polymorphic type");
+
+    PYBIND11_OBJECT(class_, generic_type, PyType_Check)
+
+    template <typename... Extra>
+    class_(handle scope, const char *name, const Extra &... extra) {
+        using namespace detail;
+
+        // MI can only be specified via class_ template options, not constructor parameters
+        static_assert(
+            none_of<is_pyobject<Extra>...>::value || // no base class arguments, or:
+            (   constexpr_sum(is_pyobject<Extra>::value...) == 1 && // Exactly one base
+                constexpr_sum(is_base<options>::value...)   == 0 && // no template option bases
+                none_of<std::is_same<multiple_inheritance, Extra>...>::value), // no multiple_inheritance attr
+            "Error: multiple inheritance bases must be specified via class_ template options");
+
+        type_record record;
+        record.scope = scope;
+        record.name = name;
+        record.type = &typeid(type);
+        record.type_size = sizeof(conditional_t<has_alias, type_alias, type>);
+        record.holder_size = sizeof(holder_type);
+        record.init_instance = init_instance;
+        record.dealloc = dealloc;
+        record.default_holder = std::is_same<holder_type, std::unique_ptr<type>>::value;
+
+        set_operator_new<type>(&record);
+
+        /* Register base classes specified via template arguments to class_, if any */
+        PYBIND11_EXPAND_SIDE_EFFECTS(add_base<options>(record));
+
+        /* Process optional arguments, if any */
+        process_attributes<Extra...>::init(extra..., &record);
+
+        generic_type::initialize(record);
+
+        if (has_alias) {
+            auto &instances = record.module_local ? registered_local_types_cpp() : get_internals().registered_types_cpp;
+            instances[std::type_index(typeid(type_alias))] = instances[std::type_index(typeid(type))];
+        }
+    }
+
+    template <typename Base, detail::enable_if_t<is_base<Base>::value, int> = 0>
+    static void add_base(detail::type_record &rec) {
+        rec.add_base(typeid(Base), [](void *src) -> void * {
+            return static_cast<Base *>(reinterpret_cast<type *>(src));
+        });
+    }
+
+    template <typename Base, detail::enable_if_t<!is_base<Base>::value, int> = 0>
+    static void add_base(detail::type_record &) { }
+
+    template <typename Func, typename... Extra>
+    class_ &def(const char *name_, Func&& f, const Extra&... extra) {
+        cpp_function cf(method_adaptor<type>(std::forward<Func>(f)), name(name_), is_method(*this),
+                        sibling(getattr(*this, name_, none())), extra...);
+        attr(cf.name()) = cf;
+        return *this;
+    }
+
+    template <typename Func, typename... Extra> class_ &
+    def_static(const char *name_, Func &&f, const Extra&... extra) {
+        static_assert(!std::is_member_function_pointer<Func>::value,
+                "def_static(...) called with a non-static member function pointer");
+        cpp_function cf(std::forward<Func>(f), name(name_), scope(*this),
+                        sibling(getattr(*this, name_, none())), extra...);
+        attr(cf.name()) = cf;
+        return *this;
+    }
+
+    template <detail::op_id id, detail::op_type ot, typename L, typename R, typename... Extra>
+    class_ &def(const detail::op_<id, ot, L, R> &op, const Extra&... extra) {
+        op.execute(*this, extra...);
+        return *this;
+    }
+
+    template <detail::op_id id, detail::op_type ot, typename L, typename R, typename... Extra>
+    class_ & def_cast(const detail::op_<id, ot, L, R> &op, const Extra&... extra) {
+        op.execute_cast(*this, extra...);
+        return *this;
+    }
+
+    template <typename... Args, typename... Extra>
+    class_ &def(const detail::initimpl::constructor<Args...> &init, const Extra&... extra) {
+        init.execute(*this, extra...);
+        return *this;
+    }
+
+    template <typename... Args, typename... Extra>
+    class_ &def(const detail::initimpl::alias_constructor<Args...> &init, const Extra&... extra) {
+        init.execute(*this, extra...);
+        return *this;
+    }
+
+    template <typename... Args, typename... Extra>
+    class_ &def(detail::initimpl::factory<Args...> &&init, const Extra&... extra) {
+        std::move(init).execute(*this, extra...);
+        return *this;
+    }
+
+    template <typename... Args, typename... Extra>
+    class_ &def(detail::initimpl::pickle_factory<Args...> &&pf, const Extra &...extra) {
+        std::move(pf).execute(*this, extra...);
+        return *this;
+    }
+
+    template <typename Func> class_& def_buffer(Func &&func) {
+        struct capture { Func func; };
+        capture *ptr = new capture { std::forward<Func>(func) };
+        install_buffer_funcs([](PyObject *obj, void *ptr) -> buffer_info* {
+            detail::make_caster<type> caster;
+            if (!caster.load(obj, false))
+                return nullptr;
+            return new buffer_info(((capture *) ptr)->func(caster));
+        }, ptr);
+        return *this;
+    }
+
+    template <typename Return, typename Class, typename... Args>
+    class_ &def_buffer(Return (Class::*func)(Args...)) {
+        return def_buffer([func] (type &obj) { return (obj.*func)(); });
+    }
+
+    template <typename Return, typename Class, typename... Args>
+    class_ &def_buffer(Return (Class::*func)(Args...) const) {
+        return def_buffer([func] (const type &obj) { return (obj.*func)(); });
+    }
+
+    template <typename C, typename D, typename... Extra>
+    class_ &def_readwrite(const char *name, D C::*pm, const Extra&... extra) {
+        static_assert(std::is_base_of<C, type>::value, "def_readwrite() requires a class member (or base class member)");
+        cpp_function fget([pm](const type &c) -> const D &{ return c.*pm; }, is_method(*this)),
+                     fset([pm](type &c, const D &value) { c.*pm = value; }, is_method(*this));
+        def_property(name, fget, fset, return_value_policy::reference_internal, extra...);
+        return *this;
+    }
+
+    template <typename C, typename D, typename... Extra>
+    class_ &def_readonly(const char *name, const D C::*pm, const Extra& ...extra) {
+        static_assert(std::is_base_of<C, type>::value, "def_readonly() requires a class member (or base class member)");
+        cpp_function fget([pm](const type &c) -> const D &{ return c.*pm; }, is_method(*this));
+        def_property_readonly(name, fget, return_value_policy::reference_internal, extra...);
+        return *this;
+    }
+
+    template <typename D, typename... Extra>
+    class_ &def_readwrite_static(const char *name, D *pm, const Extra& ...extra) {
+        cpp_function fget([pm](object) -> const D &{ return *pm; }, scope(*this)),
+                     fset([pm](object, const D &value) { *pm = value; }, scope(*this));
+        def_property_static(name, fget, fset, return_value_policy::reference, extra...);
+        return *this;
+    }
+
+    template <typename D, typename... Extra>
+    class_ &def_readonly_static(const char *name, const D *pm, const Extra& ...extra) {
+        cpp_function fget([pm](object) -> const D &{ return *pm; }, scope(*this));
+        def_property_readonly_static(name, fget, return_value_policy::reference, extra...);
+        return *this;
+    }
+
+    /// Uses return_value_policy::reference_internal by default
+    template <typename Getter, typename... Extra>
+    class_ &def_property_readonly(const char *name, const Getter &fget, const Extra& ...extra) {
+        return def_property_readonly(name, cpp_function(method_adaptor<type>(fget)),
+                                     return_value_policy::reference_internal, extra...);
+    }
+
+    /// Uses cpp_function's return_value_policy by default
+    template <typename... Extra>
+    class_ &def_property_readonly(const char *name, const cpp_function &fget, const Extra& ...extra) {
+        return def_property(name, fget, nullptr, extra...);
+    }
+
+    /// Uses return_value_policy::reference by default
+    template <typename Getter, typename... Extra>
+    class_ &def_property_readonly_static(const char *name, const Getter &fget, const Extra& ...extra) {
+        return def_property_readonly_static(name, cpp_function(fget), return_value_policy::reference, extra...);
+    }
+
+    /// Uses cpp_function's return_value_policy by default
+    template <typename... Extra>
+    class_ &def_property_readonly_static(const char *name, const cpp_function &fget, const Extra& ...extra) {
+        return def_property_static(name, fget, nullptr, extra...);
+    }
+
+    /// Uses return_value_policy::reference_internal by default
+    template <typename Getter, typename Setter, typename... Extra>
+    class_ &def_property(const char *name, const Getter &fget, const Setter &fset, const Extra& ...extra) {
+        return def_property(name, fget, cpp_function(method_adaptor<type>(fset)), extra...);
+    }
+    template <typename Getter, typename... Extra>
+    class_ &def_property(const char *name, const Getter &fget, const cpp_function &fset, const Extra& ...extra) {
+        return def_property(name, cpp_function(method_adaptor<type>(fget)), fset,
+                            return_value_policy::reference_internal, extra...);
+    }
+
+    /// Uses cpp_function's return_value_policy by default
+    template <typename... Extra>
+    class_ &def_property(const char *name, const cpp_function &fget, const cpp_function &fset, const Extra& ...extra) {
+        return def_property_static(name, fget, fset, is_method(*this), extra...);
+    }
+
+    /// Uses return_value_policy::reference by default
+    template <typename Getter, typename... Extra>
+    class_ &def_property_static(const char *name, const Getter &fget, const cpp_function &fset, const Extra& ...extra) {
+        return def_property_static(name, cpp_function(fget), fset, return_value_policy::reference, extra...);
+    }
+
+    /// Uses cpp_function's return_value_policy by default
+    template <typename... Extra>
+    class_ &def_property_static(const char *name, const cpp_function &fget, const cpp_function &fset, const Extra& ...extra) {
+        auto rec_fget = get_function_record(fget), rec_fset = get_function_record(fset);
+        auto *rec_active = rec_fget;
+        if (rec_fget) {
+           char *doc_prev = rec_fget->doc; /* 'extra' field may include a property-specific documentation string */
+           detail::process_attributes<Extra...>::init(extra..., rec_fget);
+           if (rec_fget->doc && rec_fget->doc != doc_prev) {
+              free(doc_prev);
+              rec_fget->doc = strdup(rec_fget->doc);
+           }
+        }
+        if (rec_fset) {
+            char *doc_prev = rec_fset->doc;
+            detail::process_attributes<Extra...>::init(extra..., rec_fset);
+            if (rec_fset->doc && rec_fset->doc != doc_prev) {
+                free(doc_prev);
+                rec_fset->doc = strdup(rec_fset->doc);
+            }
+            if (! rec_active) rec_active = rec_fset;
+        }
+        def_property_static_impl(name, fget, fset, rec_active);
+        return *this;
+    }
+
+private:
+    /// Initialize holder object, variant 1: object derives from enable_shared_from_this
+    template <typename T>
+    static void init_holder(detail::instance *inst, detail::value_and_holder &v_h,
+            const holder_type * /* unused */, const std::enable_shared_from_this<T> * /* dummy */) {
+        try {
+            auto sh = std::dynamic_pointer_cast<typename holder_type::element_type>(
+                    v_h.value_ptr<type>()->shared_from_this());
+            if (sh) {
+                new (&v_h.holder<holder_type>()) holder_type(std::move(sh));
+                v_h.set_holder_constructed();
+            }
+        } catch (const std::bad_weak_ptr &) {}
+
+        if (!v_h.holder_constructed() && inst->owned) {
+            new (&v_h.holder<holder_type>()) holder_type(v_h.value_ptr<type>());
+            v_h.set_holder_constructed();
+        }
+    }
+
+    static void init_holder_from_existing(const detail::value_and_holder &v_h,
+            const holder_type *holder_ptr, std::true_type /*is_copy_constructible*/) {
+        new (&v_h.holder<holder_type>()) holder_type(*reinterpret_cast<const holder_type *>(holder_ptr));
+    }
+
+    static void init_holder_from_existing(const detail::value_and_holder &v_h,
+            const holder_type *holder_ptr, std::false_type /*is_copy_constructible*/) {
+        new (&v_h.holder<holder_type>()) holder_type(std::move(*const_cast<holder_type *>(holder_ptr)));
+    }
+
+    /// Initialize holder object, variant 2: try to construct from existing holder object, if possible
+    static void init_holder(detail::instance *inst, detail::value_and_holder &v_h,
+            const holder_type *holder_ptr, const void * /* dummy -- not enable_shared_from_this<T>) */) {
+        if (holder_ptr) {
+            init_holder_from_existing(v_h, holder_ptr, std::is_copy_constructible<holder_type>());
+            v_h.set_holder_constructed();
+        } else if (inst->owned || detail::always_construct_holder<holder_type>::value) {
+            new (&v_h.holder<holder_type>()) holder_type(v_h.value_ptr<type>());
+            v_h.set_holder_constructed();
+        }
+    }
+
+    /// Performs instance initialization including constructing a holder and registering the known
+    /// instance.  Should be called as soon as the `type` value_ptr is set for an instance.  Takes an
+    /// optional pointer to an existing holder to use; if not specified and the instance is
+    /// `.owned`, a new holder will be constructed to manage the value pointer.
+    static void init_instance(detail::instance *inst, const void *holder_ptr) {
+        auto v_h = inst->get_value_and_holder(detail::get_type_info(typeid(type)));
+        if (!v_h.instance_registered()) {
+            register_instance(inst, v_h.value_ptr(), v_h.type);
+            v_h.set_instance_registered();
+        }
+        init_holder(inst, v_h, (const holder_type *) holder_ptr, v_h.value_ptr<type>());
+    }
+
+    /// Deallocates an instance; via holder, if constructed; otherwise via operator delete.
+    static void dealloc(detail::value_and_holder &v_h) {
+        if (v_h.holder_constructed()) {
+            v_h.holder<holder_type>().~holder_type();
+            v_h.set_holder_constructed(false);
+        }
+        else {
+            detail::call_operator_delete(v_h.value_ptr<type>(), v_h.type->type_size);
+        }
+        v_h.value_ptr() = nullptr;
+    }
+
+    static detail::function_record *get_function_record(handle h) {
+        h = detail::get_function(h);
+        return h ? (detail::function_record *) reinterpret_borrow<capsule>(PyCFunction_GET_SELF(h.ptr()))
+                 : nullptr;
+    }
+};
+
+/// Binds an existing constructor taking arguments Args...
+template <typename... Args> detail::initimpl::constructor<Args...> init() { return {}; }
+/// Like `init<Args...>()`, but the instance is always constructed through the alias class (even
+/// when not inheriting on the Python side).
+template <typename... Args> detail::initimpl::alias_constructor<Args...> init_alias() { return {}; }
+
+/// Binds a factory function as a constructor
+template <typename Func, typename Ret = detail::initimpl::factory<Func>>
+Ret init(Func &&f) { return {std::forward<Func>(f)}; }
+
+/// Dual-argument factory function: the first function is called when no alias is needed, the second
+/// when an alias is needed (i.e. due to python-side inheritance).  Arguments must be identical.
+template <typename CFunc, typename AFunc, typename Ret = detail::initimpl::factory<CFunc, AFunc>>
+Ret init(CFunc &&c, AFunc &&a) {
+    return {std::forward<CFunc>(c), std::forward<AFunc>(a)};
+}
+
+/// Binds pickling functions `__getstate__` and `__setstate__` and ensures that the type
+/// returned by `__getstate__` is the same as the argument accepted by `__setstate__`.
+template <typename GetState, typename SetState>
+detail::initimpl::pickle_factory<GetState, SetState> pickle(GetState &&g, SetState &&s) {
+    return {std::forward<GetState>(g), std::forward<SetState>(s)};
+}
+
+/// Binds C++ enumerations and enumeration classes to Python
+template <typename Type> class enum_ : public class_<Type> {
+public:
+    using class_<Type>::def;
+    using class_<Type>::def_property_readonly_static;
+    using Scalar = typename std::underlying_type<Type>::type;
+
+    template <typename... Extra>
+    enum_(const handle &scope, const char *name, const Extra&... extra)
+      : class_<Type>(scope, name, extra...), m_entries(), m_parent(scope) {
+
+        constexpr bool is_arithmetic = detail::any_of<std::is_same<arithmetic, Extra>...>::value;
+
+        auto m_entries_ptr = m_entries.inc_ref().ptr();
+        def("__repr__", [name, m_entries_ptr](Type value) -> pybind11::str {
+            for (const auto &kv : reinterpret_borrow<dict>(m_entries_ptr)) {
+                if (pybind11::cast<Type>(kv.second[int_(0)]) == value)
+                    return pybind11::str("{}.{}").format(name, kv.first);
+            }
+            return pybind11::str("{}.???").format(name);
+        });
+        def_property_readonly_static("__doc__", [m_entries_ptr](handle self) {
+            std::string docstring;
+            const char *tp_doc = ((PyTypeObject *) self.ptr())->tp_doc;
+            if (tp_doc)
+                docstring += std::string(tp_doc) + "\n\n";
+            docstring += "Members:";
+            for (const auto &kv : reinterpret_borrow<dict>(m_entries_ptr)) {
+                auto key = std::string(pybind11::str(kv.first));
+                auto comment = kv.second[int_(1)];
+                docstring += "\n\n  " + key;
+                if (!comment.is_none())
+                    docstring += " : " + (std::string) pybind11::str(comment);
+            }
+            return docstring;
+        });
+        def_property_readonly_static("__members__", [m_entries_ptr](handle /* self */) {
+            dict m;
+            for (const auto &kv : reinterpret_borrow<dict>(m_entries_ptr))
+                m[kv.first] = kv.second[int_(0)];
+            return m;
+        }, return_value_policy::copy);
+        def(init([](Scalar i) { return static_cast<Type>(i); }));
+        def("__int__", [](Type value) { return (Scalar) value; });
+        #if PY_MAJOR_VERSION < 3
+            def("__long__", [](Type value) { return (Scalar) value; });
+        #endif
+        def("__eq__", [](const Type &value, Type *value2) { return value2 && value == *value2; });
+        def("__ne__", [](const Type &value, Type *value2) { return !value2 || value != *value2; });
+        if (is_arithmetic) {
+            def("__lt__", [](const Type &value, Type *value2) { return value2 && value < *value2; });
+            def("__gt__", [](const Type &value, Type *value2) { return value2 && value > *value2; });
+            def("__le__", [](const Type &value, Type *value2) { return value2 && value <= *value2; });
+            def("__ge__", [](const Type &value, Type *value2) { return value2 && value >= *value2; });
+        }
+        if (std::is_convertible<Type, Scalar>::value) {
+            // Don't provide comparison with the underlying type if the enum isn't convertible,
+            // i.e. if Type is a scoped enum, mirroring the C++ behaviour.  (NB: we explicitly
+            // convert Type to Scalar below anyway because this needs to compile).
+            def("__eq__", [](const Type &value, Scalar value2) { return (Scalar) value == value2; });
+            def("__ne__", [](const Type &value, Scalar value2) { return (Scalar) value != value2; });
+            if (is_arithmetic) {
+                def("__lt__", [](const Type &value, Scalar value2) { return (Scalar) value < value2; });
+                def("__gt__", [](const Type &value, Scalar value2) { return (Scalar) value > value2; });
+                def("__le__", [](const Type &value, Scalar value2) { return (Scalar) value <= value2; });
+                def("__ge__", [](const Type &value, Scalar value2) { return (Scalar) value >= value2; });
+                def("__invert__", [](const Type &value) { return ~((Scalar) value); });
+                def("__and__", [](const Type &value, Scalar value2) { return (Scalar) value & value2; });
+                def("__or__", [](const Type &value, Scalar value2) { return (Scalar) value | value2; });
+                def("__xor__", [](const Type &value, Scalar value2) { return (Scalar) value ^ value2; });
+                def("__rand__", [](const Type &value, Scalar value2) { return (Scalar) value & value2; });
+                def("__ror__", [](const Type &value, Scalar value2) { return (Scalar) value | value2; });
+                def("__rxor__", [](const Type &value, Scalar value2) { return (Scalar) value ^ value2; });
+                def("__and__", [](const Type &value, const Type &value2) { return (Scalar) value & (Scalar) value2; });
+                def("__or__", [](const Type &value, const Type &value2) { return (Scalar) value | (Scalar) value2; });
+                def("__xor__", [](const Type &value, const Type &value2) { return (Scalar) value ^ (Scalar) value2; });
+            }
+        }
+        def("__hash__", [](const Type &value) { return (Scalar) value; });
+        // Pickling and unpickling -- needed for use with the 'multiprocessing' module
+        def(pickle([](const Type &value) { return pybind11::make_tuple((Scalar) value); },
+                   [](tuple t) { return static_cast<Type>(t[0].cast<Scalar>()); }));
+    }
+
+    /// Export enumeration entries into the parent scope
+    enum_& export_values() {
+        for (const auto &kv : m_entries)
+            m_parent.attr(kv.first) = kv.second[int_(0)];
+        return *this;
+    }
+
+    /// Add an enumeration entry
+    enum_& value(char const* name, Type value, const char *doc = nullptr) {
+        auto v = pybind11::cast(value, return_value_policy::copy);
+        this->attr(name) = v;
+        m_entries[pybind11::str(name)] = std::make_pair(v, doc);
+        return *this;
+    }
+
+private:
+    dict m_entries;
+    handle m_parent;
+};
+
+NAMESPACE_BEGIN(detail)
+
+
+inline void keep_alive_impl(handle nurse, handle patient) {
+    if (!nurse || !patient)
+        pybind11_fail("Could not activate keep_alive!");
+
+    if (patient.is_none() || nurse.is_none())
+        return; /* Nothing to keep alive or nothing to be kept alive by */
+
+    auto tinfo = all_type_info(Py_TYPE(nurse.ptr()));
+    if (!tinfo.empty()) {
+        /* It's a pybind-registered type, so we can store the patient in the
+         * internal list. */
+        add_patient(nurse.ptr(), patient.ptr());
+    }
+    else {
+        /* Fall back to clever approach based on weak references taken from
+         * Boost.Python. This is not used for pybind-registered types because
+         * the objects can be destroyed out-of-order in a GC pass. */
+        cpp_function disable_lifesupport(
+            [patient](handle weakref) { patient.dec_ref(); weakref.dec_ref(); });
+
+        weakref wr(nurse, disable_lifesupport);
+
+        patient.inc_ref(); /* reference patient and leak the weak reference */
+        (void) wr.release();
+    }
+}
+
+PYBIND11_NOINLINE inline void keep_alive_impl(size_t Nurse, size_t Patient, function_call &call, handle ret) {
+    auto get_arg = [&](size_t n) {
+        if (n == 0)
+            return ret;
+        else if (n == 1 && call.init_self)
+            return call.init_self;
+        else if (n <= call.args.size())
+            return call.args[n - 1];
+        return handle();
+    };
+
+    keep_alive_impl(get_arg(Nurse), get_arg(Patient));
+}
+
+inline std::pair<decltype(internals::registered_types_py)::iterator, bool> all_type_info_get_cache(PyTypeObject *type) {
+    auto res = get_internals().registered_types_py
+#ifdef __cpp_lib_unordered_map_try_emplace
+        .try_emplace(type);
+#else
+        .emplace(type, std::vector<detail::type_info *>());
+#endif
+    if (res.second) {
+        // New cache entry created; set up a weak reference to automatically remove it if the type
+        // gets destroyed:
+        weakref((PyObject *) type, cpp_function([type](handle wr) {
+            get_internals().registered_types_py.erase(type);
+            wr.dec_ref();
+        })).release();
+    }
+
+    return res;
+}
+
+template <typename Iterator, typename Sentinel, bool KeyIterator, return_value_policy Policy>
+struct iterator_state {
+    Iterator it;
+    Sentinel end;
+    bool first_or_done;
+};
+
+NAMESPACE_END(detail)
+
+/// Makes a python iterator from a first and past-the-end C++ InputIterator.
+template <return_value_policy Policy = return_value_policy::reference_internal,
+          typename Iterator,
+          typename Sentinel,
+          typename ValueType = decltype(*std::declval<Iterator>()),
+          typename... Extra>
+iterator make_iterator(Iterator first, Sentinel last, Extra &&... extra) {
+    typedef detail::iterator_state<Iterator, Sentinel, false, Policy> state;
+
+    if (!detail::get_type_info(typeid(state), false)) {
+        class_<state>(handle(), "iterator", pybind11::module_local())
+            .def("__iter__", [](state &s) -> state& { return s; })
+            .def("__next__", [](state &s) -> ValueType {
+                if (!s.first_or_done)
+                    ++s.it;
+                else
+                    s.first_or_done = false;
+                if (s.it == s.end) {
+                    s.first_or_done = true;
+                    throw stop_iteration();
+                }
+                return *s.it;
+            }, std::forward<Extra>(extra)..., Policy);
+    }
+
+    return cast(state{first, last, true});
+}
+
+/// Makes an python iterator over the keys (`.first`) of a iterator over pairs from a
+/// first and past-the-end InputIterator.
+template <return_value_policy Policy = return_value_policy::reference_internal,
+          typename Iterator,
+          typename Sentinel,
+          typename KeyType = decltype((*std::declval<Iterator>()).first),
+          typename... Extra>
+iterator make_key_iterator(Iterator first, Sentinel last, Extra &&... extra) {
+    typedef detail::iterator_state<Iterator, Sentinel, true, Policy> state;
+
+    if (!detail::get_type_info(typeid(state), false)) {
+        class_<state>(handle(), "iterator", pybind11::module_local())
+            .def("__iter__", [](state &s) -> state& { return s; })
+            .def("__next__", [](state &s) -> KeyType {
+                if (!s.first_or_done)
+                    ++s.it;
+                else
+                    s.first_or_done = false;
+                if (s.it == s.end) {
+                    s.first_or_done = true;
+                    throw stop_iteration();
+                }
+                return (*s.it).first;
+            }, std::forward<Extra>(extra)..., Policy);
+    }
+
+    return cast(state{first, last, true});
+}
+
+/// Makes an iterator over values of an stl container or other container supporting
+/// `std::begin()`/`std::end()`
+template <return_value_policy Policy = return_value_policy::reference_internal,
+          typename Type, typename... Extra> iterator make_iterator(Type &value, Extra&&... extra) {
+    return make_iterator<Policy>(std::begin(value), std::end(value), extra...);
+}
+
+/// Makes an iterator over the keys (`.first`) of a stl map-like container supporting
+/// `std::begin()`/`std::end()`
+template <return_value_policy Policy = return_value_policy::reference_internal,
+          typename Type, typename... Extra> iterator make_key_iterator(Type &value, Extra&&... extra) {
+    return make_key_iterator<Policy>(std::begin(value), std::end(value), extra...);
+}
+
+template <typename InputType, typename OutputType> void implicitly_convertible() {
+    struct set_flag {
+        bool &flag;
+        set_flag(bool &flag) : flag(flag) { flag = true; }
+        ~set_flag() { flag = false; }
+    };
+    auto implicit_caster = [](PyObject *obj, PyTypeObject *type) -> PyObject * {
+        static bool currently_used = false;
+        if (currently_used) // implicit conversions are non-reentrant
+            return nullptr;
+        set_flag flag_helper(currently_used);
+        if (!detail::make_caster<InputType>().load(obj, false))
+            return nullptr;
+        tuple args(1);
+        args[0] = obj;
+        PyObject *result = PyObject_Call((PyObject *) type, args.ptr(), nullptr);
+        if (result == nullptr)
+            PyErr_Clear();
+        return result;
+    };
+
+    if (auto tinfo = detail::get_type_info(typeid(OutputType)))
+        tinfo->implicit_conversions.push_back(implicit_caster);
+    else
+        pybind11_fail("implicitly_convertible: Unable to find type " + type_id<OutputType>());
+}
+
+template <typename ExceptionTranslator>
+void register_exception_translator(ExceptionTranslator&& translator) {
+    detail::get_internals().registered_exception_translators.push_front(
+        std::forward<ExceptionTranslator>(translator));
+}
+
+/**
+ * Wrapper to generate a new Python exception type.
+ *
+ * This should only be used with PyErr_SetString for now.
+ * It is not (yet) possible to use as a py::base.
+ * Template type argument is reserved for future use.
+ */
+template <typename type>
+class exception : public object {
+public:
+    exception(handle scope, const char *name, PyObject *base = PyExc_Exception) {
+        std::string full_name = scope.attr("__name__").cast<std::string>() +
+                                std::string(".") + name;
+        m_ptr = PyErr_NewException(const_cast<char *>(full_name.c_str()), base, NULL);
+        if (hasattr(scope, name))
+            pybind11_fail("Error during initialization: multiple incompatible "
+                          "definitions with name \"" + std::string(name) + "\"");
+        scope.attr(name) = *this;
+    }
+
+    // Sets the current python exception to this exception object with the given message
+    void operator()(const char *message) {
+        PyErr_SetString(m_ptr, message);
+    }
+};
+
+/**
+ * Registers a Python exception in `m` of the given `name` and installs an exception translator to
+ * translate the C++ exception to the created Python exception using the exceptions what() method.
+ * This is intended for simple exception translations; for more complex translation, register the
+ * exception object and translator directly.
+ */
+template <typename CppException>
+exception<CppException> &register_exception(handle scope,
+                                            const char *name,
+                                            PyObject *base = PyExc_Exception) {
+    static exception<CppException> ex(scope, name, base);
+    register_exception_translator([](std::exception_ptr p) {
+        if (!p) return;
+        try {
+            std::rethrow_exception(p);
+        } catch (const CppException &e) {
+            ex(e.what());
+        }
+    });
+    return ex;
+}
+
+NAMESPACE_BEGIN(detail)
+PYBIND11_NOINLINE inline void print(tuple args, dict kwargs) {
+    auto strings = tuple(args.size());
+    for (size_t i = 0; i < args.size(); ++i) {
+        strings[i] = str(args[i]);
+    }
+    auto sep = kwargs.contains("sep") ? kwargs["sep"] : cast(" ");
+    auto line = sep.attr("join")(strings);
+
+    object file;
+    if (kwargs.contains("file")) {
+        file = kwargs["file"].cast<object>();
+    } else {
+        try {
+            file = module::import("sys").attr("stdout");
+        } catch (const error_already_set &) {
+            /* If print() is called from code that is executed as
+               part of garbage collection during interpreter shutdown,
+               importing 'sys' can fail. Give up rather than crashing the
+               interpreter in this case. */
+            return;
+        }
+    }
+
+    auto write = file.attr("write");
+    write(line);
+    write(kwargs.contains("end") ? kwargs["end"] : cast("\n"));
+
+    if (kwargs.contains("flush") && kwargs["flush"].cast<bool>())
+        file.attr("flush")();
+}
+NAMESPACE_END(detail)
+
+template <return_value_policy policy = return_value_policy::automatic_reference, typename... Args>
+void print(Args &&...args) {
+    auto c = detail::collect_arguments<policy>(std::forward<Args>(args)...);
+    detail::print(c.args(), c.kwargs());
+}
+
+#if defined(WITH_THREAD) && !defined(PYPY_VERSION)
+
+/* The functions below essentially reproduce the PyGILState_* API using a RAII
+ * pattern, but there are a few important differences:
+ *
+ * 1. When acquiring the GIL from an non-main thread during the finalization
+ *    phase, the GILState API blindly terminates the calling thread, which
+ *    is often not what is wanted. This API does not do this.
+ *
+ * 2. The gil_scoped_release function can optionally cut the relationship
+ *    of a PyThreadState and its associated thread, which allows moving it to
+ *    another thread (this is a fairly rare/advanced use case).
+ *
+ * 3. The reference count of an acquired thread state can be controlled. This
+ *    can be handy to prevent cases where callbacks issued from an external
+ *    thread would otherwise constantly construct and destroy thread state data
+ *    structures.
+ *
+ * See the Python bindings of NanoGUI (http://github.com/wjakob/nanogui) for an
+ * example which uses features 2 and 3 to migrate the Python thread of
+ * execution to another thread (to run the event loop on the original thread,
+ * in this case).
+ */
+
+class gil_scoped_acquire {
+public:
+    PYBIND11_NOINLINE gil_scoped_acquire() {
+        auto const &internals = detail::get_internals();
+        tstate = (PyThreadState *) PyThread_get_key_value(internals.tstate);
+
+        if (!tstate) {
+            tstate = PyThreadState_New(internals.istate);
+            #if !defined(NDEBUG)
+                if (!tstate)
+                    pybind11_fail("scoped_acquire: could not create thread state!");
+            #endif
+            tstate->gilstate_counter = 0;
+            #if PY_MAJOR_VERSION < 3
+                PyThread_delete_key_value(internals.tstate);
+            #endif
+            PyThread_set_key_value(internals.tstate, tstate);
+        } else {
+            release = detail::get_thread_state_unchecked() != tstate;
+        }
+
+        if (release) {
+            /* Work around an annoying assertion in PyThreadState_Swap */
+            #if defined(Py_DEBUG)
+                PyInterpreterState *interp = tstate->interp;
+                tstate->interp = nullptr;
+            #endif
+            PyEval_AcquireThread(tstate);
+            #if defined(Py_DEBUG)
+                tstate->interp = interp;
+            #endif
+        }
+
+        inc_ref();
+    }
+
+    void inc_ref() {
+        ++tstate->gilstate_counter;
+    }
+
+    PYBIND11_NOINLINE void dec_ref() {
+        --tstate->gilstate_counter;
+        #if !defined(NDEBUG)
+            if (detail::get_thread_state_unchecked() != tstate)
+                pybind11_fail("scoped_acquire::dec_ref(): thread state must be current!");
+            if (tstate->gilstate_counter < 0)
+                pybind11_fail("scoped_acquire::dec_ref(): reference count underflow!");
+        #endif
+        if (tstate->gilstate_counter == 0) {
+            #if !defined(NDEBUG)
+                if (!release)
+                    pybind11_fail("scoped_acquire::dec_ref(): internal error!");
+            #endif
+            PyThreadState_Clear(tstate);
+            PyThreadState_DeleteCurrent();
+            PyThread_delete_key_value(detail::get_internals().tstate);
+            release = false;
+        }
+    }
+
+    PYBIND11_NOINLINE ~gil_scoped_acquire() {
+        dec_ref();
+        if (release)
+           PyEval_SaveThread();
+    }
+private:
+    PyThreadState *tstate = nullptr;
+    bool release = true;
+};
+
+class gil_scoped_release {
+public:
+    explicit gil_scoped_release(bool disassoc = false) : disassoc(disassoc) {
+        // `get_internals()` must be called here unconditionally in order to initialize
+        // `internals.tstate` for subsequent `gil_scoped_acquire` calls. Otherwise, an
+        // initialization race could occur as multiple threads try `gil_scoped_acquire`.
+        const auto &internals = detail::get_internals();
+        tstate = PyEval_SaveThread();
+        if (disassoc) {
+            auto key = internals.tstate;
+            #if PY_MAJOR_VERSION < 3
+                PyThread_delete_key_value(key);
+            #else
+                PyThread_set_key_value(key, nullptr);
+            #endif
+        }
+    }
+    ~gil_scoped_release() {
+        if (!tstate)
+            return;
+        PyEval_RestoreThread(tstate);
+        if (disassoc) {
+            auto key = detail::get_internals().tstate;
+            #if PY_MAJOR_VERSION < 3
+                PyThread_delete_key_value(key);
+            #endif
+            PyThread_set_key_value(key, tstate);
+        }
+    }
+private:
+    PyThreadState *tstate;
+    bool disassoc;
+};
+#elif defined(PYPY_VERSION)
+class gil_scoped_acquire {
+    PyGILState_STATE state;
+public:
+    gil_scoped_acquire() { state = PyGILState_Ensure(); }
+    ~gil_scoped_acquire() { PyGILState_Release(state); }
+};
+
+class gil_scoped_release {
+    PyThreadState *state;
+public:
+    gil_scoped_release() { state = PyEval_SaveThread(); }
+    ~gil_scoped_release() { PyEval_RestoreThread(state); }
+};
+#else
+class gil_scoped_acquire { };
+class gil_scoped_release { };
+#endif
+
+error_already_set::~error_already_set() {
+    if (type) {
+        gil_scoped_acquire gil;
+        type.release().dec_ref();
+        value.release().dec_ref();
+        trace.release().dec_ref();
+    }
+}
+
+inline function get_type_overload(const void *this_ptr, const detail::type_info *this_type, const char *name)  {
+    handle self = detail::get_object_handle(this_ptr, this_type);
+    if (!self)
+        return function();
+    handle type = self.get_type();
+    auto key = std::make_pair(type.ptr(), name);
+
+    /* Cache functions that aren't overloaded in Python to avoid
+       many costly Python dictionary lookups below */
+    auto &cache = detail::get_internals().inactive_overload_cache;
+    if (cache.find(key) != cache.end())
+        return function();
+
+    function overload = getattr(self, name, function());
+    if (overload.is_cpp_function()) {
+        cache.insert(key);
+        return function();
+    }
+
+    /* Don't call dispatch code if invoked from overridden function.
+       Unfortunately this doesn't work on PyPy. */
+#if !defined(PYPY_VERSION)
+    PyFrameObject *frame = PyThreadState_Get()->frame;
+    if (frame && (std::string) str(frame->f_code->co_name) == name &&
+        frame->f_code->co_argcount > 0) {
+        PyFrame_FastToLocals(frame);
+        PyObject *self_caller = PyDict_GetItem(
+            frame->f_locals, PyTuple_GET_ITEM(frame->f_code->co_varnames, 0));
+        if (self_caller == self.ptr())
+            return function();
+    }
+#else
+    /* PyPy currently doesn't provide a detailed cpyext emulation of
+       frame objects, so we have to emulate this using Python. This
+       is going to be slow..*/
+    dict d; d["self"] = self; d["name"] = pybind11::str(name);
+    PyObject *result = PyRun_String(
+        "import inspect\n"
+        "frame = inspect.currentframe()\n"
+        "if frame is not None:\n"
+        "    frame = frame.f_back\n"
+        "    if frame is not None and str(frame.f_code.co_name) == name and "
+        "frame.f_code.co_argcount > 0:\n"
+        "        self_caller = frame.f_locals[frame.f_code.co_varnames[0]]\n"
+        "        if self_caller == self:\n"
+        "            self = None\n",
+        Py_file_input, d.ptr(), d.ptr());
+    if (result == nullptr)
+        throw error_already_set();
+    if (d["self"].is_none())
+        return function();
+    Py_DECREF(result);
+#endif
+
+    return overload;
+}
+
+template <class T> function get_overload(const T *this_ptr, const char *name) {
+    auto tinfo = detail::get_type_info(typeid(T));
+    return tinfo ? get_type_overload(this_ptr, tinfo, name) : function();
+}
+
+#define PYBIND11_OVERLOAD_INT(ret_type, cname, name, ...) { \
+        pybind11::gil_scoped_acquire gil; \
+        pybind11::function overload = pybind11::get_overload(static_cast<const cname *>(this), name); \
+        if (overload) { \
+            auto o = overload(__VA_ARGS__); \
+            if (pybind11::detail::cast_is_temporary_value_reference<ret_type>::value) { \
+                static pybind11::detail::overload_caster_t<ret_type> caster; \
+                return pybind11::detail::cast_ref<ret_type>(std::move(o), caster); \
+            } \
+            else return pybind11::detail::cast_safe<ret_type>(std::move(o)); \
+        } \
+    }
+
+#define PYBIND11_OVERLOAD_NAME(ret_type, cname, name, fn, ...) \
+    PYBIND11_OVERLOAD_INT(ret_type, cname, name, __VA_ARGS__) \
+    return cname::fn(__VA_ARGS__)
+
+#define PYBIND11_OVERLOAD_PURE_NAME(ret_type, cname, name, fn, ...) \
+    PYBIND11_OVERLOAD_INT(ret_type, cname, name, __VA_ARGS__) \
+    pybind11::pybind11_fail("Tried to call pure virtual function \"" #cname "::" name "\"");
+
+#define PYBIND11_OVERLOAD(ret_type, cname, fn, ...) \
+    PYBIND11_OVERLOAD_NAME(ret_type, cname, #fn, fn, __VA_ARGS__)
+
+#define PYBIND11_OVERLOAD_PURE(ret_type, cname, fn, ...) \
+    PYBIND11_OVERLOAD_PURE_NAME(ret_type, cname, #fn, fn, __VA_ARGS__)
+
+NAMESPACE_END(PYBIND11_NAMESPACE)
+
+#if defined(_MSC_VER)
+#  pragma warning(pop)
+#elif defined(__INTEL_COMPILER)
+/* Leave ignored warnings on */
+#elif defined(__GNUG__) && !defined(__clang__)
+#  pragma GCC diagnostic pop
+#endif

dlib/external/pybind11/include/pybind11/pytypes.h

+/*
+    pybind11/pytypes.h: Convenience wrapper classes for basic Python types
+
+    Copyright (c) 2016 Wenzel Jakob <wenzel.jakob@epfl.ch>
+
+    All rights reserved. Use of this source code is governed by a
+    BSD-style license that can be found in the LICENSE file.
+*/
+
+#pragma once
+
+#include "detail/common.h"
+#include "buffer_info.h"
+#include <utility>
+#include <type_traits>
+
+NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
+
+/* A few forward declarations */
+class handle; class object;
+class str; class iterator;
+struct arg; struct arg_v;
+
+NAMESPACE_BEGIN(detail)
+class args_proxy;
+inline bool isinstance_generic(handle obj, const std::type_info &tp);
+
+// Accessor forward declarations
+template <typename Policy> class accessor;
+namespace accessor_policies {
+    struct obj_attr;
+    struct str_attr;
+    struct generic_item;
+    struct sequence_item;
+    struct list_item;
+    struct tuple_item;
+}
+using obj_attr_accessor = accessor<accessor_policies::obj_attr>;
+using str_attr_accessor = accessor<accessor_policies::str_attr>;
+using item_accessor = accessor<accessor_policies::generic_item>;
+using sequence_accessor = accessor<accessor_policies::sequence_item>;
+using list_accessor = accessor<accessor_policies::list_item>;
+using tuple_accessor = accessor<accessor_policies::tuple_item>;
+
+/// Tag and check to identify a class which implements the Python object API
+class pyobject_tag { };
+template <typename T> using is_pyobject = std::is_base_of<pyobject_tag, remove_reference_t<T>>;
+
+/** \rst
+    A mixin class which adds common functions to `handle`, `object` and various accessors.
+    The only requirement for `Derived` is to implement ``PyObject *Derived::ptr() const``.
+\endrst */
+template <typename Derived>
+class object_api : public pyobject_tag {
+    const Derived &derived() const { return static_cast<const Derived &>(*this); }
+
+public:
+    /** \rst
+        Return an iterator equivalent to calling ``iter()`` in Python. The object
+        must be a collection which supports the iteration protocol.
+    \endrst */
+    iterator begin() const;
+    /// Return a sentinel which ends iteration.
+    iterator end() const;
+
+    /** \rst
+        Return an internal functor to invoke the object's sequence protocol. Casting
+        the returned ``detail::item_accessor`` instance to a `handle` or `object`
+        subclass causes a corresponding call to ``__getitem__``. Assigning a `handle`
+        or `object` subclass causes a call to ``__setitem__``.
+    \endrst */
+    item_accessor operator[](handle key) const;
+    /// See above (the only difference is that they key is provided as a string literal)
+    item_accessor operator[](const char *key) const;
+
+    /** \rst
+        Return an internal functor to access the object's attributes. Casting the
+        returned ``detail::obj_attr_accessor`` instance to a `handle` or `object`
+        subclass causes a corresponding call to ``getattr``. Assigning a `handle`
+        or `object` subclass causes a call to ``setattr``.
+    \endrst */
+    obj_attr_accessor attr(handle key) const;
+    /// See above (the only difference is that they key is provided as a string literal)
+    str_attr_accessor attr(const char *key) const;
+
+    /** \rst
+        Matches * unpacking in Python, e.g. to unpack arguments out of a ``tuple``
+        or ``list`` for a function call. Applying another * to the result yields
+        ** unpacking, e.g. to unpack a dict as function keyword arguments.
+        See :ref:`calling_python_functions`.
+    \endrst */
+    args_proxy operator*() const;
+
+    /// Check if the given item is contained within this object, i.e. ``item in obj``.
+    template <typename T> bool contains(T &&item) const;
+
+    /** \rst
+        Assuming the Python object is a function or implements the ``__call__``
+        protocol, ``operator()`` invokes the underlying function, passing an
+        arbitrary set of parameters. The result is returned as a `object` and
+        may need to be converted back into a Python object using `handle::cast()`.
+
+        When some of the arguments cannot be converted to Python objects, the
+        function will throw a `cast_error` exception. When the Python function
+        call fails, a `error_already_set` exception is thrown.
+    \endrst */
+    template <return_value_policy policy = return_value_policy::automatic_reference, typename... Args>
+    object operator()(Args &&...args) const;
+    template <return_value_policy policy = return_value_policy::automatic_reference, typename... Args>
+    PYBIND11_DEPRECATED("call(...) was deprecated in favor of operator()(...)")
+        object call(Args&&... args) const;
+
+    /// Equivalent to ``obj is other`` in Python.
+    bool is(object_api const& other) const { return derived().ptr() == other.derived().ptr(); }
+    /// Equivalent to ``obj is None`` in Python.
+    bool is_none() const { return derived().ptr() == Py_None; }
+    PYBIND11_DEPRECATED("Use py::str(obj) instead")
+    pybind11::str str() const;
+
+    /// Get or set the object's docstring, i.e. ``obj.__doc__``.
+    str_attr_accessor doc() const;
+
+    /// Return the object's current reference count
+    int ref_count() const { return static_cast<int>(Py_REFCNT(derived().ptr())); }
+    /// Return a handle to the Python type object underlying the instance
+    handle get_type() const;
+};
+
+NAMESPACE_END(detail)
+
+/** \rst
+    Holds a reference to a Python object (no reference counting)
+
+    The `handle` class is a thin wrapper around an arbitrary Python object (i.e. a
+    ``PyObject *`` in Python's C API). It does not perform any automatic reference
+    counting and merely provides a basic C++ interface to various Python API functions.
+
+    .. seealso::
+        The `object` class inherits from `handle` and adds automatic reference
+        counting features.
+\endrst */
+class handle : public detail::object_api<handle> {
+public:
+    /// The default constructor creates a handle with a ``nullptr``-valued pointer
+    handle() = default;
+    /// Creates a ``handle`` from the given raw Python object pointer
+    handle(PyObject *ptr) : m_ptr(ptr) { } // Allow implicit conversion from PyObject*
+
+    /// Return the underlying ``PyObject *`` pointer
+    PyObject *ptr() const { return m_ptr; }
+    PyObject *&ptr() { return m_ptr; }
+
+    /** \rst
+        Manually increase the reference count of the Python object. Usually, it is
+        preferable to use the `object` class which derives from `handle` and calls
+        this function automatically. Returns a reference to itself.
+    \endrst */
+    const handle& inc_ref() const & { Py_XINCREF(m_ptr); return *this; }
+
+    /** \rst
+        Manually decrease the reference count of the Python object. Usually, it is
+        preferable to use the `object` class which derives from `handle` and calls
+        this function automatically. Returns a reference to itself.
+    \endrst */
+    const handle& dec_ref() const & { Py_XDECREF(m_ptr); return *this; }
+
+    /** \rst
+        Attempt to cast the Python object into the given C++ type. A `cast_error`
+        will be throw upon failure.
+    \endrst */
+    template <typename T> T cast() const;
+    /// Return ``true`` when the `handle` wraps a valid Python object
+    explicit operator bool() const { return m_ptr != nullptr; }
+    /** \rst
+        Deprecated: Check that the underlying pointers are the same.
+        Equivalent to ``obj1 is obj2`` in Python.
+    \endrst */
+    PYBIND11_DEPRECATED("Use obj1.is(obj2) instead")
+    bool operator==(const handle &h) const { return m_ptr == h.m_ptr; }
+    PYBIND11_DEPRECATED("Use !obj1.is(obj2) instead")
+    bool operator!=(const handle &h) const { return m_ptr != h.m_ptr; }
+    PYBIND11_DEPRECATED("Use handle::operator bool() instead")
+    bool check() const { return m_ptr != nullptr; }
+protected:
+    PyObject *m_ptr = nullptr;
+};
+
+/** \rst
+    Holds a reference to a Python object (with reference counting)
+
+    Like `handle`, the `object` class is a thin wrapper around an arbitrary Python
+    object (i.e. a ``PyObject *`` in Python's C API). In contrast to `handle`, it
+    optionally increases the object's reference count upon construction, and it
+    *always* decreases the reference count when the `object` instance goes out of
+    scope and is destructed. When using `object` instances consistently, it is much
+    easier to get reference counting right at the first attempt.
+\endrst */
+class object : public handle {
+public:
+    object() = default;
+    PYBIND11_DEPRECATED("Use reinterpret_borrow<object>() or reinterpret_steal<object>()")
+    object(handle h, bool is_borrowed) : handle(h) { if (is_borrowed) inc_ref(); }
+    /// Copy constructor; always increases the reference count
+    object(const object &o) : handle(o) { inc_ref(); }
+    /// Move constructor; steals the object from ``other`` and preserves its reference count
+    object(object &&other) noexcept { m_ptr = other.m_ptr; other.m_ptr = nullptr; }
+    /// Destructor; automatically calls `handle::dec_ref()`
+    ~object() { dec_ref(); }
+
+    /** \rst
+        Resets the internal pointer to ``nullptr`` without without decreasing the
+        object's reference count. The function returns a raw handle to the original
+        Python object.
+    \endrst */
+    handle release() {
+      PyObject *tmp = m_ptr;
+      m_ptr = nullptr;
+      return handle(tmp);
+    }
+
+    object& operator=(const object &other) {
+        other.inc_ref();
+        dec_ref();
+        m_ptr = other.m_ptr;
+        return *this;
+    }
+
+    object& operator=(object &&other) noexcept {
+        if (this != &other) {
+            handle temp(m_ptr);
+            m_ptr = other.m_ptr;
+            other.m_ptr = nullptr;
+            temp.dec_ref();
+        }
+        return *this;
+    }
+
+    // Calling cast() on an object lvalue just copies (via handle::cast)
+    template <typename T> T cast() const &;
+    // Calling on an object rvalue does a move, if needed and/or possible
+    template <typename T> T cast() &&;
+
+protected:
+    // Tags for choosing constructors from raw PyObject *
+    struct borrowed_t { };
+    struct stolen_t { };
+
+    template <typename T> friend T reinterpret_borrow(handle);
+    template <typename T> friend T reinterpret_steal(handle);
+
+public:
+    // Only accessible from derived classes and the reinterpret_* functions
+    object(handle h, borrowed_t) : handle(h) { inc_ref(); }
+    object(handle h, stolen_t) : handle(h) { }
+};
+
+/** \rst
+    Declare that a `handle` or ``PyObject *`` is a certain type and borrow the reference.
+    The target type ``T`` must be `object` or one of its derived classes. The function
+    doesn't do any conversions or checks. It's up to the user to make sure that the
+    target type is correct.
+
+    .. code-block:: cpp
+
+        PyObject *p = PyList_GetItem(obj, index);
+        py::object o = reinterpret_borrow<py::object>(p);
+        // or
+        py::tuple t = reinterpret_borrow<py::tuple>(p); // <-- `p` must be already be a `tuple`
+\endrst */
+template <typename T> T reinterpret_borrow(handle h) { return {h, object::borrowed_t{}}; }
+
+/** \rst
+    Like `reinterpret_borrow`, but steals the reference.
+
+     .. code-block:: cpp
+
+        PyObject *p = PyObject_Str(obj);
+        py::str s = reinterpret_steal<py::str>(p); // <-- `p` must be already be a `str`
+\endrst */
+template <typename T> T reinterpret_steal(handle h) { return {h, object::stolen_t{}}; }
+
+NAMESPACE_BEGIN(detail)
+inline std::string error_string();
+NAMESPACE_END(detail)
+
+/// Fetch and hold an error which was already set in Python.  An instance of this is typically
+/// thrown to propagate python-side errors back through C++ which can either be caught manually or
+/// else falls back to the function dispatcher (which then raises the captured error back to
+/// python).
+class error_already_set : public std::runtime_error {
+public:
+    /// Constructs a new exception from the current Python error indicator, if any.  The current
+    /// Python error indicator will be cleared.
+    error_already_set() : std::runtime_error(detail::error_string()) {
+        PyErr_Fetch(&type.ptr(), &value.ptr(), &trace.ptr());
+    }
+
+    error_already_set(const error_already_set &) = default;
+    error_already_set(error_already_set &&) = default;
+
+    inline ~error_already_set();
+
+    /// Give the currently-held error back to Python, if any.  If there is currently a Python error
+    /// already set it is cleared first.  After this call, the current object no longer stores the
+    /// error variables (but the `.what()` string is still available).
+    void restore() { PyErr_Restore(type.release().ptr(), value.release().ptr(), trace.release().ptr()); }
+
+    // Does nothing; provided for backwards compatibility.
+    PYBIND11_DEPRECATED("Use of error_already_set.clear() is deprecated")
+    void clear() {}
+
+    /// Check if the currently trapped error type matches the given Python exception class (or a
+    /// subclass thereof).  May also be passed a tuple to search for any exception class matches in
+    /// the given tuple.
+    bool matches(handle ex) const { return PyErr_GivenExceptionMatches(ex.ptr(), type.ptr()); }
+
+private:
+    object type, value, trace;
+};
+
+/** \defgroup python_builtins _
+    Unless stated otherwise, the following C++ functions behave the same
+    as their Python counterparts.
+ */
+
+/** \ingroup python_builtins
+    \rst
+    Return true if ``obj`` is an instance of ``T``. Type ``T`` must be a subclass of
+    `object` or a class which was exposed to Python as ``py::class_<T>``.
+\endrst */
+template <typename T, detail::enable_if_t<std::is_base_of<object, T>::value, int> = 0>
+bool isinstance(handle obj) { return T::check_(obj); }
+
+template <typename T, detail::enable_if_t<!std::is_base_of<object, T>::value, int> = 0>
+bool isinstance(handle obj) { return detail::isinstance_generic(obj, typeid(T)); }
+
+template <> inline bool isinstance<handle>(handle obj) = delete;
+template <> inline bool isinstance<object>(handle obj) { return obj.ptr() != nullptr; }
+
+/// \ingroup python_builtins
+/// Return true if ``obj`` is an instance of the ``type``.
+inline bool isinstance(handle obj, handle type) {
+    const auto result = PyObject_IsInstance(obj.ptr(), type.ptr());
+    if (result == -1)
+        throw error_already_set();
+    return result != 0;
+}
+
+/// \addtogroup python_builtins
+/// @{
+inline bool hasattr(handle obj, handle name) {
+    return PyObject_HasAttr(obj.ptr(), name.ptr()) == 1;
+}
+
+inline bool hasattr(handle obj, const char *name) {
+    return PyObject_HasAttrString(obj.ptr(), name) == 1;
+}
+
+inline object getattr(handle obj, handle name) {
+    PyObject *result = PyObject_GetAttr(obj.ptr(), name.ptr());
+    if (!result) { throw error_already_set(); }
+    return reinterpret_steal<object>(result);
+}
+
+inline object getattr(handle obj, const char *name) {
+    PyObject *result = PyObject_GetAttrString(obj.ptr(), name);
+    if (!result) { throw error_already_set(); }
+    return reinterpret_steal<object>(result);
+}
+
+inline object getattr(handle obj, handle name, handle default_) {
+    if (PyObject *result = PyObject_GetAttr(obj.ptr(), name.ptr())) {
+        return reinterpret_steal<object>(result);
+    } else {
+        PyErr_Clear();
+        return reinterpret_borrow<object>(default_);
+    }
+}
+
+inline object getattr(handle obj, const char *name, handle default_) {
+    if (PyObject *result = PyObject_GetAttrString(obj.ptr(), name)) {
+        return reinterpret_steal<object>(result);
+    } else {
+        PyErr_Clear();
+        return reinterpret_borrow<object>(default_);
+    }
+}
+
+inline void setattr(handle obj, handle name, handle value) {
+    if (PyObject_SetAttr(obj.ptr(), name.ptr(), value.ptr()) != 0) { throw error_already_set(); }
+}
+
+inline void setattr(handle obj, const char *name, handle value) {
+    if (PyObject_SetAttrString(obj.ptr(), name, value.ptr()) != 0) { throw error_already_set(); }
+}
+
+inline ssize_t hash(handle obj) {
+    auto h = PyObject_Hash(obj.ptr());
+    if (h == -1) { throw error_already_set(); }
+    return h;
+}
+
+/// @} python_builtins
+
+NAMESPACE_BEGIN(detail)
+inline handle get_function(handle value) {
+    if (value) {
+#if PY_MAJOR_VERSION >= 3
+        if (PyInstanceMethod_Check(value.ptr()))
+            value = PyInstanceMethod_GET_FUNCTION(value.ptr());
+        else
+#endif
+        if (PyMethod_Check(value.ptr()))
+            value = PyMethod_GET_FUNCTION(value.ptr());
+    }
+    return value;
+}
+
+// Helper aliases/functions to support implicit casting of values given to python accessors/methods.
+// When given a pyobject, this simply returns the pyobject as-is; for other C++ type, the value goes
+// through pybind11::cast(obj) to convert it to an `object`.
+template <typename T, enable_if_t<is_pyobject<T>::value, int> = 0>
+auto object_or_cast(T &&o) -> decltype(std::forward<T>(o)) { return std::forward<T>(o); }
+// The following casting version is implemented in cast.h:
+template <typename T, enable_if_t<!is_pyobject<T>::value, int> = 0>
+object object_or_cast(T &&o);
+// Match a PyObject*, which we want to convert directly to handle via its converting constructor
+inline handle object_or_cast(PyObject *ptr) { return ptr; }
+
+
+template <typename Policy>
+class accessor : public object_api<accessor<Policy>> {
+    using key_type = typename Policy::key_type;
+
+public:
+    accessor(handle obj, key_type key) : obj(obj), key(std::move(key)) { }
+    accessor(const accessor &) = default;
+    accessor(accessor &&) = default;
+
+    // accessor overload required to override default assignment operator (templates are not allowed
+    // to replace default compiler-generated assignments).
+    void operator=(const accessor &a) && { std::move(*this).operator=(handle(a)); }
+    void operator=(const accessor &a) & { operator=(handle(a)); }
+
+    template <typename T> void operator=(T &&value) && {
+        Policy::set(obj, key, object_or_cast(std::forward<T>(value)));
+    }
+    template <typename T> void operator=(T &&value) & {
+        get_cache() = reinterpret_borrow<object>(object_or_cast(std::forward<T>(value)));
+    }
+
+    template <typename T = Policy>
+    PYBIND11_DEPRECATED("Use of obj.attr(...) as bool is deprecated in favor of pybind11::hasattr(obj, ...)")
+    explicit operator enable_if_t<std::is_same<T, accessor_policies::str_attr>::value ||
+            std::is_same<T, accessor_policies::obj_attr>::value, bool>() const {
+        return hasattr(obj, key);
+    }
+    template <typename T = Policy>
+    PYBIND11_DEPRECATED("Use of obj[key] as bool is deprecated in favor of obj.contains(key)")
+    explicit operator enable_if_t<std::is_same<T, accessor_policies::generic_item>::value, bool>() const {
+        return obj.contains(key);
+    }
+
+    operator object() const { return get_cache(); }
+    PyObject *ptr() const { return get_cache().ptr(); }
+    template <typename T> T cast() const { return get_cache().template cast<T>(); }
+
+private:
+    object &get_cache() const {
+        if (!cache) { cache = Policy::get(obj, key); }
+        return cache;
+    }
+
+private:
+    handle obj;
+    key_type key;
+    mutable object cache;
+};
+
+NAMESPACE_BEGIN(accessor_policies)
+struct obj_attr {
+    using key_type = object;
+    static object get(handle obj, handle key) { return getattr(obj, key); }
+    static void set(handle obj, handle key, handle val) { setattr(obj, key, val); }
+};
+
+struct str_attr {
+    using key_type = const char *;
+    static object get(handle obj, const char *key) { return getattr(obj, key); }
+    static void set(handle obj, const char *key, handle val) { setattr(obj, key, val); }
+};
+
+struct generic_item {
+    using key_type = object;
+
+    static object get(handle obj, handle key) {
+        PyObject *result = PyObject_GetItem(obj.ptr(), key.ptr());
+        if (!result) { throw error_already_set(); }
+        return reinterpret_steal<object>(result);
+    }
+
+    static void set(handle obj, handle key, handle val) {
+        if (PyObject_SetItem(obj.ptr(), key.ptr(), val.ptr()) != 0) { throw error_already_set(); }
+    }
+};
+
+struct sequence_item {
+    using key_type = size_t;
+
+    static object get(handle obj, size_t index) {
+        PyObject *result = PySequence_GetItem(obj.ptr(), static_cast<ssize_t>(index));
+        if (!result) { throw error_already_set(); }
+        return reinterpret_steal<object>(result);
+    }
+
+    static void set(handle obj, size_t index, handle val) {
+        // PySequence_SetItem does not steal a reference to 'val'
+        if (PySequence_SetItem(obj.ptr(), static_cast<ssize_t>(index), val.ptr()) != 0) {
+            throw error_already_set();
+        }
+    }
+};
+
+struct list_item {
+    using key_type = size_t;
+
+    static object get(handle obj, size_t index) {
+        PyObject *result = PyList_GetItem(obj.ptr(), static_cast<ssize_t>(index));
+        if (!result) { throw error_already_set(); }
+        return reinterpret_borrow<object>(result);
+    }
+
+    static void set(handle obj, size_t index, handle val) {
+        // PyList_SetItem steals a reference to 'val'
+        if (PyList_SetItem(obj.ptr(), static_cast<ssize_t>(index), val.inc_ref().ptr()) != 0) {
+            throw error_already_set();
+        }
+    }
+};
+
+struct tuple_item {
+    using key_type = size_t;
+
+    static object get(handle obj, size_t index) {
+        PyObject *result = PyTuple_GetItem(obj.ptr(), static_cast<ssize_t>(index));
+        if (!result) { throw error_already_set(); }
+        return reinterpret_borrow<object>(result);
+    }
+
+    static void set(handle obj, size_t index, handle val) {
+        // PyTuple_SetItem steals a reference to 'val'
+        if (PyTuple_SetItem(obj.ptr(), static_cast<ssize_t>(index), val.inc_ref().ptr()) != 0) {
+            throw error_already_set();
+        }
+    }
+};
+NAMESPACE_END(accessor_policies)
+
+/// STL iterator template used for tuple, list, sequence and dict
+template <typename Policy>
+class generic_iterator : public Policy {
+    using It = generic_iterator;
+
+public:
+    using difference_type = ssize_t;
+    using iterator_category = typename Policy::iterator_category;
+    using value_type = typename Policy::value_type;
+    using reference = typename Policy::reference;
+    using pointer = typename Policy::pointer;
+
+    generic_iterator() = default;
+    generic_iterator(handle seq, ssize_t index) : Policy(seq, index) { }
+
+    reference operator*() const { return Policy::dereference(); }
+    reference operator[](difference_type n) const { return *(*this + n); }
+    pointer operator->() const { return **this; }
+
+    It &operator++() { Policy::increment(); return *this; }
+    It operator++(int) { auto copy = *this; Policy::increment(); return copy; }
+    It &operator--() { Policy::decrement(); return *this; }
+    It operator--(int) { auto copy = *this; Policy::decrement(); return copy; }
+    It &operator+=(difference_type n) { Policy::advance(n); return *this; }
+    It &operator-=(difference_type n) { Policy::advance(-n); return *this; }
+
+    friend It operator+(const It &a, difference_type n) { auto copy = a; return copy += n; }
+    friend It operator+(difference_type n, const It &b) { return b + n; }
+    friend It operator-(const It &a, difference_type n) { auto copy = a; return copy -= n; }
+    friend difference_type operator-(const It &a, const It &b) { return a.distance_to(b); }
+
+    friend bool operator==(const It &a, const It &b) { return a.equal(b); }
+    friend bool operator!=(const It &a, const It &b) { return !(a == b); }
+    friend bool operator< (const It &a, const It &b) { return b - a > 0; }
+    friend bool operator> (const It &a, const It &b) { return b < a; }
+    friend bool operator>=(const It &a, const It &b) { return !(a < b); }
+    friend bool operator<=(const It &a, const It &b) { return !(a > b); }
+};
+
+NAMESPACE_BEGIN(iterator_policies)
+/// Quick proxy class needed to implement ``operator->`` for iterators which can't return pointers
+template <typename T>
+struct arrow_proxy {
+    T value;
+
+    arrow_proxy(T &&value) : value(std::move(value)) { }
+    T *operator->() const { return &value; }
+};
+
+/// Lightweight iterator policy using just a simple pointer: see ``PySequence_Fast_ITEMS``
+class sequence_fast_readonly {
+protected:
+    using iterator_category = std::random_access_iterator_tag;
+    using value_type = handle;
+    using reference = const handle;
+    using pointer = arrow_proxy<const handle>;
+
+    sequence_fast_readonly(handle obj, ssize_t n) : ptr(PySequence_Fast_ITEMS(obj.ptr()) + n) { }
+
+    reference dereference() const { return *ptr; }
+    void increment() { ++ptr; }
+    void decrement() { --ptr; }
+    void advance(ssize_t n) { ptr += n; }
+    bool equal(const sequence_fast_readonly &b) const { return ptr == b.ptr; }
+    ssize_t distance_to(const sequence_fast_readonly &b) const { return ptr - b.ptr; }
+
+private:
+    PyObject **ptr;
+};
+
+/// Full read and write access using the sequence protocol: see ``detail::sequence_accessor``
+class sequence_slow_readwrite {
+protected:
+    using iterator_category = std::random_access_iterator_tag;
+    using value_type = object;
+    using reference = sequence_accessor;
+    using pointer = arrow_proxy<const sequence_accessor>;
+
+    sequence_slow_readwrite(handle obj, ssize_t index) : obj(obj), index(index) { }
+
+    reference dereference() const { return {obj, static_cast<size_t>(index)}; }
+    void increment() { ++index; }
+    void decrement() { --index; }
+    void advance(ssize_t n) { index += n; }
+    bool equal(const sequence_slow_readwrite &b) const { return index == b.index; }
+    ssize_t distance_to(const sequence_slow_readwrite &b) const { return index - b.index; }
+
+private:
+    handle obj;
+    ssize_t index;
+};
+
+/// Python's dictionary protocol permits this to be a forward iterator
+class dict_readonly {
+protected:
+    using iterator_category = std::forward_iterator_tag;
+    using value_type = std::pair<handle, handle>;
+    using reference = const value_type;
+    using pointer = arrow_proxy<const value_type>;
+
+    dict_readonly() = default;
+    dict_readonly(handle obj, ssize_t pos) : obj(obj), pos(pos) { increment(); }
+
+    reference dereference() const { return {key, value}; }
+    void increment() { if (!PyDict_Next(obj.ptr(), &pos, &key, &value)) { pos = -1; } }
+    bool equal(const dict_readonly &b) const { return pos == b.pos; }
+
+private:
+    handle obj;
+    PyObject *key, *value;
+    ssize_t pos = -1;
+};
+NAMESPACE_END(iterator_policies)
+
+#if !defined(PYPY_VERSION)
+using tuple_iterator = generic_iterator<iterator_policies::sequence_fast_readonly>;
+using list_iterator = generic_iterator<iterator_policies::sequence_fast_readonly>;
+#else
+using tuple_iterator = generic_iterator<iterator_policies::sequence_slow_readwrite>;
+using list_iterator = generic_iterator<iterator_policies::sequence_slow_readwrite>;
+#endif
+
+using sequence_iterator = generic_iterator<iterator_policies::sequence_slow_readwrite>;
+using dict_iterator = generic_iterator<iterator_policies::dict_readonly>;
+
+inline bool PyIterable_Check(PyObject *obj) {
+    PyObject *iter = PyObject_GetIter(obj);
+    if (iter) {
+        Py_DECREF(iter);
+        return true;
+    } else {
+        PyErr_Clear();
+        return false;
+    }
+}
+
+inline bool PyNone_Check(PyObject *o) { return o == Py_None; }
+
+inline bool PyUnicode_Check_Permissive(PyObject *o) { return PyUnicode_Check(o) || PYBIND11_BYTES_CHECK(o); }
+
+class kwargs_proxy : public handle {
+public:
+    explicit kwargs_proxy(handle h) : handle(h) { }
+};
+
+class args_proxy : public handle {
+public:
+    explicit args_proxy(handle h) : handle(h) { }
+    kwargs_proxy operator*() const { return kwargs_proxy(*this); }
+};
+
+/// Python argument categories (using PEP 448 terms)
+template <typename T> using is_keyword = std::is_base_of<arg, T>;
+template <typename T> using is_s_unpacking = std::is_same<args_proxy, T>; // * unpacking
+template <typename T> using is_ds_unpacking = std::is_same<kwargs_proxy, T>; // ** unpacking
+template <typename T> using is_positional = satisfies_none_of<T,
+    is_keyword, is_s_unpacking, is_ds_unpacking
+>;
+template <typename T> using is_keyword_or_ds = satisfies_any_of<T, is_keyword, is_ds_unpacking>;
+
+// Call argument collector forward declarations
+template <return_value_policy policy = return_value_policy::automatic_reference>
+class simple_collector;
+template <return_value_policy policy = return_value_policy::automatic_reference>
+class unpacking_collector;
+
+NAMESPACE_END(detail)
+
+// TODO: After the deprecated constructors are removed, this macro can be simplified by
+//       inheriting ctors: `using Parent::Parent`. It's not an option right now because
+//       the `using` statement triggers the parent deprecation warning even if the ctor
+//       isn't even used.
+#define PYBIND11_OBJECT_COMMON(Name, Parent, CheckFun) \
+    public: \
+        PYBIND11_DEPRECATED("Use reinterpret_borrow<"#Name">() or reinterpret_steal<"#Name">()") \
+        Name(handle h, bool is_borrowed) : Parent(is_borrowed ? Parent(h, borrowed_t{}) : Parent(h, stolen_t{})) { } \
+        Name(handle h, borrowed_t) : Parent(h, borrowed_t{}) { } \
+        Name(handle h, stolen_t) : Parent(h, stolen_t{}) { } \
+        PYBIND11_DEPRECATED("Use py::isinstance<py::python_type>(obj) instead") \
+        bool check() const { return m_ptr != nullptr && (bool) CheckFun(m_ptr); } \
+        static bool check_(handle h) { return h.ptr() != nullptr && CheckFun(h.ptr()); }
+
+#define PYBIND11_OBJECT_CVT(Name, Parent, CheckFun, ConvertFun) \
+    PYBIND11_OBJECT_COMMON(Name, Parent, CheckFun) \
+    /* This is deliberately not 'explicit' to allow implicit conversion from object: */ \
+    Name(const object &o) \
+    : Parent(check_(o) ? o.inc_ref().ptr() : ConvertFun(o.ptr()), stolen_t{}) \
+    { if (!m_ptr) throw error_already_set(); } \
+    Name(object &&o) \
+    : Parent(check_(o) ? o.release().ptr() : ConvertFun(o.ptr()), stolen_t{}) \
+    { if (!m_ptr) throw error_already_set(); } \
+    template <typename Policy_> \
+    Name(const ::pybind11::detail::accessor<Policy_> &a) : Name(object(a)) { }
+
+#define PYBIND11_OBJECT(Name, Parent, CheckFun) \
+    PYBIND11_OBJECT_COMMON(Name, Parent, CheckFun) \
+    /* This is deliberately not 'explicit' to allow implicit conversion from object: */ \
+    Name(const object &o) : Parent(o) { } \
+    Name(object &&o) : Parent(std::move(o)) { }
+
+#define PYBIND11_OBJECT_DEFAULT(Name, Parent, CheckFun) \
+    PYBIND11_OBJECT(Name, Parent, CheckFun) \
+    Name() : Parent() { }
+
+/// \addtogroup pytypes
+/// @{
+
+/** \rst
+    Wraps a Python iterator so that it can also be used as a C++ input iterator
+
+    Caveat: copying an iterator does not (and cannot) clone the internal
+    state of the Python iterable. This also applies to the post-increment
+    operator. This iterator should only be used to retrieve the current
+    value using ``operator*()``.
+\endrst */
+class iterator : public object {
+public:
+    using iterator_category = std::input_iterator_tag;
+    using difference_type = ssize_t;
+    using value_type = handle;
+    using reference = const handle;
+    using pointer = const handle *;
+
+    PYBIND11_OBJECT_DEFAULT(iterator, object, PyIter_Check)
+
+    iterator& operator++() {
+        advance();
+        return *this;
+    }
+
+    iterator operator++(int) {
+        auto rv = *this;
+        advance();
+        return rv;
+    }
+
+    reference operator*() const {
+        if (m_ptr && !value.ptr()) {
+            auto& self = const_cast<iterator &>(*this);
+            self.advance();
+        }
+        return value;
+    }
+
+    pointer operator->() const { operator*(); return &value; }
+
+    /** \rst
+         The value which marks the end of the iteration. ``it == iterator::sentinel()``
+         is equivalent to catching ``StopIteration`` in Python.
+
+         .. code-block:: cpp
+
+             void foo(py::iterator it) {
+                 while (it != py::iterator::sentinel()) {
+                    // use `*it`
+                    ++it;
+                 }
+             }
+    \endrst */
+    static iterator sentinel() { return {}; }
+
+    friend bool operator==(const iterator &a, const iterator &b) { return a->ptr() == b->ptr(); }
+    friend bool operator!=(const iterator &a, const iterator &b) { return a->ptr() != b->ptr(); }
+
+private:
+    void advance() {
+        value = reinterpret_steal<object>(PyIter_Next(m_ptr));
+        if (PyErr_Occurred()) { throw error_already_set(); }
+    }
+
+private:
+    object value = {};
+};
+
+class iterable : public object {
+public:
+    PYBIND11_OBJECT_DEFAULT(iterable, object, detail::PyIterable_Check)
+};
+
+class bytes;
+
+class str : public object {
+public:
+    PYBIND11_OBJECT_CVT(str, object, detail::PyUnicode_Check_Permissive, raw_str)
+
+    str(const char *c, size_t n)
+        : object(PyUnicode_FromStringAndSize(c, (ssize_t) n), stolen_t{}) {
+        if (!m_ptr) pybind11_fail("Could not allocate string object!");
+    }
+
+    // 'explicit' is explicitly omitted from the following constructors to allow implicit conversion to py::str from C++ string-like objects
+    str(const char *c = "")
+        : object(PyUnicode_FromString(c), stolen_t{}) {
+        if (!m_ptr) pybind11_fail("Could not allocate string object!");
+    }
+
+    str(const std::string &s) : str(s.data(), s.size()) { }
+
+    explicit str(const bytes &b);
+
+    /** \rst
+        Return a string representation of the object. This is analogous to
+        the ``str()`` function in Python.
+    \endrst */
+    explicit str(handle h) : object(raw_str(h.ptr()), stolen_t{}) { }
+
+    operator std::string() const {
+        object temp = *this;
+        if (PyUnicode_Check(m_ptr)) {
+            temp = reinterpret_steal<object>(PyUnicode_AsUTF8String(m_ptr));
+            if (!temp)
+                pybind11_fail("Unable to extract string contents! (encoding issue)");
+        }
+        char *buffer;
+        ssize_t length;
+        if (PYBIND11_BYTES_AS_STRING_AND_SIZE(temp.ptr(), &buffer, &length))
+            pybind11_fail("Unable to extract string contents! (invalid type)");
+        return std::string(buffer, (size_t) length);
+    }
+
+    template <typename... Args>
+    str format(Args &&...args) const {
+        return attr("format")(std::forward<Args>(args)...);
+    }
+
+private:
+    /// Return string representation -- always returns a new reference, even if already a str
+    static PyObject *raw_str(PyObject *op) {
+        PyObject *str_value = PyObject_Str(op);
+#if PY_MAJOR_VERSION < 3
+        if (!str_value) throw error_already_set();
+        PyObject *unicode = PyUnicode_FromEncodedObject(str_value, "utf-8", nullptr);
+        Py_XDECREF(str_value); str_value = unicode;
+#endif
+        return str_value;
+    }
+};
+/// @} pytypes
+
+inline namespace literals {
+/** \rst
+    String literal version of `str`
+ \endrst */
+inline str operator"" _s(const char *s, size_t size) { return {s, size}; }
+}
+
+/// \addtogroup pytypes
+/// @{
+class bytes : public object {
+public:
+    PYBIND11_OBJECT(bytes, object, PYBIND11_BYTES_CHECK)
+
+    // Allow implicit conversion:
+    bytes(const char *c = "")
+        : object(PYBIND11_BYTES_FROM_STRING(c), stolen_t{}) {
+        if (!m_ptr) pybind11_fail("Could not allocate bytes object!");
+    }
+
+    bytes(const char *c, size_t n)
+        : object(PYBIND11_BYTES_FROM_STRING_AND_SIZE(c, (ssize_t) n), stolen_t{}) {
+        if (!m_ptr) pybind11_fail("Could not allocate bytes object!");
+    }
+
+    // Allow implicit conversion:
+    bytes(const std::string &s) : bytes(s.data(), s.size()) { }
+
+    explicit bytes(const pybind11::str &s);
+
+    operator std::string() const {
+        char *buffer;
+        ssize_t length;
+        if (PYBIND11_BYTES_AS_STRING_AND_SIZE(m_ptr, &buffer, &length))
+            pybind11_fail("Unable to extract bytes contents!");
+        return std::string(buffer, (size_t) length);
+    }
+};
+
+inline bytes::bytes(const pybind11::str &s) {
+    object temp = s;
+    if (PyUnicode_Check(s.ptr())) {
+        temp = reinterpret_steal<object>(PyUnicode_AsUTF8String(s.ptr()));
+        if (!temp)
+            pybind11_fail("Unable to extract string contents! (encoding issue)");
+    }
+    char *buffer;
+    ssize_t length;
+    if (PYBIND11_BYTES_AS_STRING_AND_SIZE(temp.ptr(), &buffer, &length))
+        pybind11_fail("Unable to extract string contents! (invalid type)");
+    auto obj = reinterpret_steal<object>(PYBIND11_BYTES_FROM_STRING_AND_SIZE(buffer, length));
+    if (!obj)
+        pybind11_fail("Could not allocate bytes object!");
+    m_ptr = obj.release().ptr();
+}
+
+inline str::str(const bytes& b) {
+    char *buffer;
+    ssize_t length;
+    if (PYBIND11_BYTES_AS_STRING_AND_SIZE(b.ptr(), &buffer, &length))
+        pybind11_fail("Unable to extract bytes contents!");
+    auto obj = reinterpret_steal<object>(PyUnicode_FromStringAndSize(buffer, (ssize_t) length));
+    if (!obj)
+        pybind11_fail("Could not allocate string object!");
+    m_ptr = obj.release().ptr();
+}
+
+class none : public object {
+public:
+    PYBIND11_OBJECT(none, object, detail::PyNone_Check)
+    none() : object(Py_None, borrowed_t{}) { }
+};
+
+class bool_ : public object {
+public:
+    PYBIND11_OBJECT_CVT(bool_, object, PyBool_Check, raw_bool)
+    bool_() : object(Py_False, borrowed_t{}) { }
+    // Allow implicit conversion from and to `bool`:
+    bool_(bool value) : object(value ? Py_True : Py_False, borrowed_t{}) { }
+    operator bool() const { return m_ptr && PyLong_AsLong(m_ptr) != 0; }
+
+private:
+    /// Return the truth value of an object -- always returns a new reference
+    static PyObject *raw_bool(PyObject *op) {
+        const auto value = PyObject_IsTrue(op);
+        if (value == -1) return nullptr;
+        return handle(value ? Py_True : Py_False).inc_ref().ptr();
+    }
+};
+
+NAMESPACE_BEGIN(detail)
+// Converts a value to the given unsigned type.  If an error occurs, you get back (Unsigned) -1;
+// otherwise you get back the unsigned long or unsigned long long value cast to (Unsigned).
+// (The distinction is critically important when casting a returned -1 error value to some other
+// unsigned type: (A)-1 != (B)-1 when A and B are unsigned types of different sizes).
+template <typename Unsigned>
+Unsigned as_unsigned(PyObject *o) {
+    if (sizeof(Unsigned) <= sizeof(unsigned long)
+#if PY_VERSION_HEX < 0x03000000
+            || PyInt_Check(o)
+#endif
+    ) {
+        unsigned long v = PyLong_AsUnsignedLong(o);
+        return v == (unsigned long) -1 && PyErr_Occurred() ? (Unsigned) -1 : (Unsigned) v;
+    }
+    else {
+        unsigned long long v = PyLong_AsUnsignedLongLong(o);
+        return v == (unsigned long long) -1 && PyErr_Occurred() ? (Unsigned) -1 : (Unsigned) v;
+    }
+}
+NAMESPACE_END(detail)
+
+class int_ : public object {
+public:
+    PYBIND11_OBJECT_CVT(int_, object, PYBIND11_LONG_CHECK, PyNumber_Long)
+    int_() : object(PyLong_FromLong(0), stolen_t{}) { }
+    // Allow implicit conversion from C++ integral types:
+    template <typename T,
+              detail::enable_if_t<std::is_integral<T>::value, int> = 0>
+    int_(T value) {
+        if (sizeof(T) <= sizeof(long)) {
+            if (std::is_signed<T>::value)
+                m_ptr = PyLong_FromLong((long) value);
+            else
+                m_ptr = PyLong_FromUnsignedLong((unsigned long) value);
+        } else {
+            if (std::is_signed<T>::value)
+                m_ptr = PyLong_FromLongLong((long long) value);
+            else
+                m_ptr = PyLong_FromUnsignedLongLong((unsigned long long) value);
+        }
+        if (!m_ptr) pybind11_fail("Could not allocate int object!");
+    }
+
+    template <typename T,
+              detail::enable_if_t<std::is_integral<T>::value, int> = 0>
+    operator T() const {
+        return std::is_unsigned<T>::value
+            ? detail::as_unsigned<T>(m_ptr)
+            : sizeof(T) <= sizeof(long)
+              ? (T) PyLong_AsLong(m_ptr)
+              : (T) PYBIND11_LONG_AS_LONGLONG(m_ptr);
+    }
+};
+
+class float_ : public object {
+public:
+    PYBIND11_OBJECT_CVT(float_, object, PyFloat_Check, PyNumber_Float)
+    // Allow implicit conversion from float/double:
+    float_(float value) : object(PyFloat_FromDouble((double) value), stolen_t{}) {
+        if (!m_ptr) pybind11_fail("Could not allocate float object!");
+    }
+    float_(double value = .0) : object(PyFloat_FromDouble((double) value), stolen_t{}) {
+        if (!m_ptr) pybind11_fail("Could not allocate float object!");
+    }
+    operator float() const { return (float) PyFloat_AsDouble(m_ptr); }
+    operator double() const { return (double) PyFloat_AsDouble(m_ptr); }
+};
+
+class weakref : public object {
+public:
+    PYBIND11_OBJECT_DEFAULT(weakref, object, PyWeakref_Check)
+    explicit weakref(handle obj, handle callback = {})
+        : object(PyWeakref_NewRef(obj.ptr(), callback.ptr()), stolen_t{}) {
+        if (!m_ptr) pybind11_fail("Could not allocate weak reference!");
+    }
+};
+
+class slice : public object {
+public:
+    PYBIND11_OBJECT_DEFAULT(slice, object, PySlice_Check)
+    slice(ssize_t start_, ssize_t stop_, ssize_t step_) {
+        int_ start(start_), stop(stop_), step(step_);
+        m_ptr = PySlice_New(start.ptr(), stop.ptr(), step.ptr());
+        if (!m_ptr) pybind11_fail("Could not allocate slice object!");
+    }
+    bool compute(size_t length, size_t *start, size_t *stop, size_t *step,
+                 size_t *slicelength) const {
+        return PySlice_GetIndicesEx((PYBIND11_SLICE_OBJECT *) m_ptr,
+                                    (ssize_t) length, (ssize_t *) start,
+                                    (ssize_t *) stop, (ssize_t *) step,
+                                    (ssize_t *) slicelength) == 0;
+    }
+};
+
+class capsule : public object {
+public:
+    PYBIND11_OBJECT_DEFAULT(capsule, object, PyCapsule_CheckExact)
+    PYBIND11_DEPRECATED("Use reinterpret_borrow<capsule>() or reinterpret_steal<capsule>()")
+    capsule(PyObject *ptr, bool is_borrowed) : object(is_borrowed ? object(ptr, borrowed_t{}) : object(ptr, stolen_t{})) { }
+
+    explicit capsule(const void *value, const char *name = nullptr, void (*destructor)(PyObject *) = nullptr)
+        : object(PyCapsule_New(const_cast<void *>(value), name, destructor), stolen_t{}) {
+        if (!m_ptr)
+            pybind11_fail("Could not allocate capsule object!");
+    }
+
+    PYBIND11_DEPRECATED("Please pass a destructor that takes a void pointer as input")
+    capsule(const void *value, void (*destruct)(PyObject *))
+        : object(PyCapsule_New(const_cast<void*>(value), nullptr, destruct), stolen_t{}) {
+        if (!m_ptr)
+            pybind11_fail("Could not allocate capsule object!");
+    }
+
+    capsule(const void *value, void (*destructor)(void *)) {
+        m_ptr = PyCapsule_New(const_cast<void *>(value), nullptr, [](PyObject *o) {
+            auto destructor = reinterpret_cast<void (*)(void *)>(PyCapsule_GetContext(o));
+            void *ptr = PyCapsule_GetPointer(o, nullptr);
+            destructor(ptr);
+        });
+
+        if (!m_ptr)
+            pybind11_fail("Could not allocate capsule object!");
+
+        if (PyCapsule_SetContext(m_ptr, (void *) destructor) != 0)
+            pybind11_fail("Could not set capsule context!");
+    }
+
+    capsule(void (*destructor)()) {
+        m_ptr = PyCapsule_New(reinterpret_cast<void *>(destructor), nullptr, [](PyObject *o) {
+            auto destructor = reinterpret_cast<void (*)()>(PyCapsule_GetPointer(o, nullptr));
+            destructor();
+        });
+
+        if (!m_ptr)
+            pybind11_fail("Could not allocate capsule object!");
+    }
+
+    template <typename T> operator T *() const {
+        auto name = this->name();
+        T * result = static_cast<T *>(PyCapsule_GetPointer(m_ptr, name));
+        if (!result) pybind11_fail("Unable to extract capsule contents!");
+        return result;
+    }
+
+    const char *name() const { return PyCapsule_GetName(m_ptr); }
+};
+
+class tuple : public object {
+public:
+    PYBIND11_OBJECT_CVT(tuple, object, PyTuple_Check, PySequence_Tuple)
+    explicit tuple(size_t size = 0) : object(PyTuple_New((ssize_t) size), stolen_t{}) {
+        if (!m_ptr) pybind11_fail("Could not allocate tuple object!");
+    }
+    size_t size() const { return (size_t) PyTuple_Size(m_ptr); }
+    detail::tuple_accessor operator[](size_t index) const { return {*this, index}; }
+    detail::tuple_iterator begin() const { return {*this, 0}; }
+    detail::tuple_iterator end() const { return {*this, PyTuple_GET_SIZE(m_ptr)}; }
+};
+
+class dict : public object {
+public:
+    PYBIND11_OBJECT_CVT(dict, object, PyDict_Check, raw_dict)
+    dict() : object(PyDict_New(), stolen_t{}) {
+        if (!m_ptr) pybind11_fail("Could not allocate dict object!");
+    }
+    template <typename... Args,
+              typename = detail::enable_if_t<detail::all_of<detail::is_keyword_or_ds<Args>...>::value>,
+              // MSVC workaround: it can't compile an out-of-line definition, so defer the collector
+              typename collector = detail::deferred_t<detail::unpacking_collector<>, Args...>>
+    explicit dict(Args &&...args) : dict(collector(std::forward<Args>(args)...).kwargs()) { }
+
+    size_t size() const { return (size_t) PyDict_Size(m_ptr); }
+    detail::dict_iterator begin() const { return {*this, 0}; }
+    detail::dict_iterator end() const { return {}; }
+    void clear() const { PyDict_Clear(ptr()); }
+    bool contains(handle key) const { return PyDict_Contains(ptr(), key.ptr()) == 1; }
+    bool contains(const char *key) const { return PyDict_Contains(ptr(), pybind11::str(key).ptr()) == 1; }
+
+private:
+    /// Call the `dict` Python type -- always returns a new reference
+    static PyObject *raw_dict(PyObject *op) {
+        if (PyDict_Check(op))
+            return handle(op).inc_ref().ptr();
+        return PyObject_CallFunctionObjArgs((PyObject *) &PyDict_Type, op, nullptr);
+    }
+};
+
+class sequence : public object {
+public:
+    PYBIND11_OBJECT_DEFAULT(sequence, object, PySequence_Check)
+    size_t size() const { return (size_t) PySequence_Size(m_ptr); }
+    detail::sequence_accessor operator[](size_t index) const { return {*this, index}; }
+    detail::sequence_iterator begin() const { return {*this, 0}; }
+    detail::sequence_iterator end() const { return {*this, PySequence_Size(m_ptr)}; }
+};
+
+class list : public object {
+public:
+    PYBIND11_OBJECT_CVT(list, object, PyList_Check, PySequence_List)
+    explicit list(size_t size = 0) : object(PyList_New((ssize_t) size), stolen_t{}) {
+        if (!m_ptr) pybind11_fail("Could not allocate list object!");
+    }
+    size_t size() const { return (size_t) PyList_Size(m_ptr); }
+    detail::list_accessor operator[](size_t index) const { return {*this, index}; }
+    detail::list_iterator begin() const { return {*this, 0}; }
+    detail::list_iterator end() const { return {*this, PyList_GET_SIZE(m_ptr)}; }
+    template <typename T> void append(T &&val) const {
+        PyList_Append(m_ptr, detail::object_or_cast(std::forward<T>(val)).ptr());
+    }
+};
+
+class args : public tuple { PYBIND11_OBJECT_DEFAULT(args, tuple, PyTuple_Check) };
+class kwargs : public dict { PYBIND11_OBJECT_DEFAULT(kwargs, dict, PyDict_Check)  };
+
+class set : public object {
+public:
+    PYBIND11_OBJECT_CVT(set, object, PySet_Check, PySet_New)
+    set() : object(PySet_New(nullptr), stolen_t{}) {
+        if (!m_ptr) pybind11_fail("Could not allocate set object!");
+    }
+    size_t size() const { return (size_t) PySet_Size(m_ptr); }
+    template <typename T> bool add(T &&val) const {
+        return PySet_Add(m_ptr, detail::object_or_cast(std::forward<T>(val)).ptr()) == 0;
+    }
+    void clear() const { PySet_Clear(m_ptr); }
+};
+
+class function : public object {
+public:
+    PYBIND11_OBJECT_DEFAULT(function, object, PyCallable_Check)
+    handle cpp_function() const {
+        handle fun = detail::get_function(m_ptr);
+        if (fun && PyCFunction_Check(fun.ptr()))
+            return fun;
+        return handle();
+    }
+    bool is_cpp_function() const { return (bool) cpp_function(); }
+};
+
+class buffer : public object {
+public:
+    PYBIND11_OBJECT_DEFAULT(buffer, object, PyObject_CheckBuffer)
+
+    buffer_info request(bool writable = false) {
+        int flags = PyBUF_STRIDES | PyBUF_FORMAT;
+        if (writable) flags |= PyBUF_WRITABLE;
+        Py_buffer *view = new Py_buffer();
+        if (PyObject_GetBuffer(m_ptr, view, flags) != 0) {
+            delete view;
+            throw error_already_set();
+        }
+        return buffer_info(view);
+    }
+};
+
+class memoryview : public object {
+public:
+    explicit memoryview(const buffer_info& info) {
+        static Py_buffer buf { };
+        // Py_buffer uses signed sizes, strides and shape!..
+        static std::vector<Py_ssize_t> py_strides { };
+        static std::vector<Py_ssize_t> py_shape { };
+        buf.buf = info.ptr;
+        buf.itemsize = info.itemsize;
+        buf.format = const_cast<char *>(info.format.c_str());
+        buf.ndim = (int) info.ndim;
+        buf.len = info.size;
+        py_strides.clear();
+        py_shape.clear();
+        for (size_t i = 0; i < (size_t) info.ndim; ++i) {
+            py_strides.push_back(info.strides[i]);
+            py_shape.push_back(info.shape[i]);
+        }
+        buf.strides = py_strides.data();
+        buf.shape = py_shape.data();
+        buf.suboffsets = nullptr;
+        buf.readonly = false;
+        buf.internal = nullptr;
+
+        m_ptr = PyMemoryView_FromBuffer(&buf);
+        if (!m_ptr)
+            pybind11_fail("Unable to create memoryview from buffer descriptor");
+    }
+
+    PYBIND11_OBJECT_CVT(memoryview, object, PyMemoryView_Check, PyMemoryView_FromObject)
+};
+/// @} pytypes
+
+/// \addtogroup python_builtins
+/// @{
+inline size_t len(handle h) {
+    ssize_t result = PyObject_Length(h.ptr());
+    if (result < 0)
+        pybind11_fail("Unable to compute length of object");
+    return (size_t) result;
+}
+
+inline str repr(handle h) {
+    PyObject *str_value = PyObject_Repr(h.ptr());
+    if (!str_value) throw error_already_set();
+#if PY_MAJOR_VERSION < 3
+    PyObject *unicode = PyUnicode_FromEncodedObject(str_value, "utf-8", nullptr);
+    Py_XDECREF(str_value); str_value = unicode;
+    if (!str_value) throw error_already_set();
+#endif
+    return reinterpret_steal<str>(str_value);
+}
+
+inline iterator iter(handle obj) {
+    PyObject *result = PyObject_GetIter(obj.ptr());
+    if (!result) { throw error_already_set(); }
+    return reinterpret_steal<iterator>(result);
+}
+/// @} python_builtins
+
+NAMESPACE_BEGIN(detail)
+template <typename D> iterator object_api<D>::begin() const { return iter(derived()); }
+template <typename D> iterator object_api<D>::end() const { return iterator::sentinel(); }
+template <typename D> item_accessor object_api<D>::operator[](handle key) const {
+    return {derived(), reinterpret_borrow<object>(key)};
+}
+template <typename D> item_accessor object_api<D>::operator[](const char *key) const {
+    return {derived(), pybind11::str(key)};
+}
+template <typename D> obj_attr_accessor object_api<D>::attr(handle key) const {
+    return {derived(), reinterpret_borrow<object>(key)};
+}
+template <typename D> str_attr_accessor object_api<D>::attr(const char *key) const {
+    return {derived(), key};
+}
+template <typename D> args_proxy object_api<D>::operator*() const {
+    return args_proxy(derived().ptr());
+}
+template <typename D> template <typename T> bool object_api<D>::contains(T &&item) const {
+    return attr("__contains__")(std::forward<T>(item)).template cast<bool>();
+}
+
+template <typename D>
+pybind11::str object_api<D>::str() const { return pybind11::str(derived()); }
+
+template <typename D>
+str_attr_accessor object_api<D>::doc() const { return attr("__doc__"); }
+
+template <typename D>
+handle object_api<D>::get_type() const { return (PyObject *) Py_TYPE(derived().ptr()); }
+
+NAMESPACE_END(detail)
+NAMESPACE_END(PYBIND11_NAMESPACE)

dlib/external/pybind11/include/pybind11/stl.h

+/*
+    pybind11/stl.h: Transparent conversion for STL data types
+
+    Copyright (c) 2016 Wenzel Jakob <wenzel.jakob@epfl.ch>
+
+    All rights reserved. Use of this source code is governed by a
+    BSD-style license that can be found in the LICENSE file.
+*/
+
+#pragma once
+
+#include "pybind11.h"
+#include <set>
+#include <unordered_set>
+#include <map>
+#include <unordered_map>
+#include <iostream>
+#include <list>
+#include <valarray>
+
+#if defined(_MSC_VER)
+#pragma warning(push)
+#pragma warning(disable: 4127) // warning C4127: Conditional expression is constant
+#endif
+
+#ifdef __has_include
+// std::optional (but including it in c++14 mode isn't allowed)
+#  if defined(PYBIND11_CPP17) && __has_include(<optional>)
+#    include <optional>
+#    define PYBIND11_HAS_OPTIONAL 1
+#  endif
+// std::experimental::optional (but not allowed in c++11 mode)
+#  if defined(PYBIND11_CPP14) && __has_include(<experimental/optional>)
+#    include <experimental/optional>
+#    define PYBIND11_HAS_EXP_OPTIONAL 1
+#  endif
+// std::variant
+#  if defined(PYBIND11_CPP17) && __has_include(<variant>)
+#    include <variant>
+#    define PYBIND11_HAS_VARIANT 1
+#  endif
+#elif defined(_MSC_VER) && defined(PYBIND11_CPP17)
+#  include <optional>
+#  include <variant>
+#  define PYBIND11_HAS_OPTIONAL 1
+#  define PYBIND11_HAS_VARIANT 1
+#endif
+
+NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
+NAMESPACE_BEGIN(detail)
+
+/// Extracts an const lvalue reference or rvalue reference for U based on the type of T (e.g. for
+/// forwarding a container element).  Typically used indirect via forwarded_type(), below.
+template <typename T, typename U>
+using forwarded_type = conditional_t<
+    std::is_lvalue_reference<T>::value, remove_reference_t<U> &, remove_reference_t<U> &&>;
+
+/// Forwards a value U as rvalue or lvalue according to whether T is rvalue or lvalue; typically
+/// used for forwarding a container's elements.
+template <typename T, typename U>
+forwarded_type<T, U> forward_like(U &&u) {
+    return std::forward<detail::forwarded_type<T, U>>(std::forward<U>(u));
+}
+
+template <typename Type, typename Key> struct set_caster {
+    using type = Type;
+    using key_conv = make_caster<Key>;
+
+    bool load(handle src, bool convert) {
+        if (!isinstance<pybind11::set>(src))
+            return false;
+        auto s = reinterpret_borrow<pybind11::set>(src);
+        value.clear();
+        for (auto entry : s) {
+            key_conv conv;
+            if (!conv.load(entry, convert))
+                return false;
+            value.insert(cast_op<Key &&>(std::move(conv)));
+        }
+        return true;
+    }
+
+    template <typename T>
+    static handle cast(T &&src, return_value_policy policy, handle parent) {
+        pybind11::set s;
+        for (auto &&value : src) {
+            auto value_ = reinterpret_steal<object>(key_conv::cast(forward_like<T>(value), policy, parent));
+            if (!value_ || !s.add(value_))
+                return handle();
+        }
+        return s.release();
+    }
+
+    PYBIND11_TYPE_CASTER(type, _("Set[") + key_conv::name + _("]"));
+};
+
+template <typename Type, typename Key, typename Value> struct map_caster {
+    using key_conv   = make_caster<Key>;
+    using value_conv = make_caster<Value>;
+
+    bool load(handle src, bool convert) {
+        if (!isinstance<dict>(src))
+            return false;
+        auto d = reinterpret_borrow<dict>(src);
+        value.clear();
+        for (auto it : d) {
+            key_conv kconv;
+            value_conv vconv;
+            if (!kconv.load(it.first.ptr(), convert) ||
+                !vconv.load(it.second.ptr(), convert))
+                return false;
+            value.emplace(cast_op<Key &&>(std::move(kconv)), cast_op<Value &&>(std::move(vconv)));
+        }
+        return true;
+    }
+
+    template <typename T>
+    static handle cast(T &&src, return_value_policy policy, handle parent) {
+        dict d;
+        for (auto &&kv : src) {
+            auto key = reinterpret_steal<object>(key_conv::cast(forward_like<T>(kv.first), policy, parent));
+            auto value = reinterpret_steal<object>(value_conv::cast(forward_like<T>(kv.second), policy, parent));
+            if (!key || !value)
+                return handle();
+            d[key] = value;
+        }
+        return d.release();
+    }
+
+    PYBIND11_TYPE_CASTER(Type, _("Dict[") + key_conv::name + _(", ") + value_conv::name + _("]"));
+};
+
+template <typename Type, typename Value> struct list_caster {
+    using value_conv = make_caster<Value>;
+
+    bool load(handle src, bool convert) {
+        if (!isinstance<sequence>(src))
+            return false;
+        auto s = reinterpret_borrow<sequence>(src);
+        value.clear();
+        reserve_maybe(s, &value);
+        for (auto it : s) {
+            value_conv conv;
+            if (!conv.load(it, convert))
+                return false;
+            value.push_back(cast_op<Value &&>(std::move(conv)));
+        }
+        return true;
+    }
+
+private:
+    template <typename T = Type,
+              enable_if_t<std::is_same<decltype(std::declval<T>().reserve(0)), void>::value, int> = 0>
+    void reserve_maybe(sequence s, Type *) { value.reserve(s.size()); }
+    void reserve_maybe(sequence, void *) { }
+
+public:
+    template <typename T>
+    static handle cast(T &&src, return_value_policy policy, handle parent) {
+        list l(src.size());
+        size_t index = 0;
+        for (auto &&value : src) {
+            auto value_ = reinterpret_steal<object>(value_conv::cast(forward_like<T>(value), policy, parent));
+            if (!value_)
+                return handle();
+            PyList_SET_ITEM(l.ptr(), (ssize_t) index++, value_.release().ptr()); // steals a reference
+        }
+        return l.release();
+    }
+
+    PYBIND11_TYPE_CASTER(Type, _("List[") + value_conv::name + _("]"));
+};
+
+template <typename Type, typename Alloc> struct type_caster<std::vector<Type, Alloc>>
+ : list_caster<std::vector<Type, Alloc>, Type> { };
+
+template <typename Type, typename Alloc> struct type_caster<std::list<Type, Alloc>>
+ : list_caster<std::list<Type, Alloc>, Type> { };
+
+template <typename ArrayType, typename Value, bool Resizable, size_t Size = 0> struct array_caster {
+    using value_conv = make_caster<Value>;
+
+private:
+    template <bool R = Resizable>
+    bool require_size(enable_if_t<R, size_t> size) {
+        if (value.size() != size)
+            value.resize(size);
+        return true;
+    }
+    template <bool R = Resizable>
+    bool require_size(enable_if_t<!R, size_t> size) {
+        return size == Size;
+    }
+
+public:
+    bool load(handle src, bool convert) {
+        if (!isinstance<list>(src))
+            return false;
+        auto l = reinterpret_borrow<list>(src);
+        if (!require_size(l.size()))
+            return false;
+        size_t ctr = 0;
+        for (auto it : l) {
+            value_conv conv;
+            if (!conv.load(it, convert))
+                return false;
+            value[ctr++] = cast_op<Value &&>(std::move(conv));
+        }
+        return true;
+    }
+
+    template <typename T>
+    static handle cast(T &&src, return_value_policy policy, handle parent) {
+        list l(src.size());
+        size_t index = 0;
+        for (auto &&value : src) {
+            auto value_ = reinterpret_steal<object>(value_conv::cast(forward_like<T>(value), policy, parent));
+            if (!value_)
+                return handle();
+            PyList_SET_ITEM(l.ptr(), (ssize_t) index++, value_.release().ptr()); // steals a reference
+        }
+        return l.release();
+    }
+
+    PYBIND11_TYPE_CASTER(ArrayType, _("List[") + value_conv::name + _<Resizable>(_(""), _("[") + _<Size>() + _("]")) + _("]"));
+};
+
+template <typename Type, size_t Size> struct type_caster<std::array<Type, Size>>
+ : array_caster<std::array<Type, Size>, Type, false, Size> { };
+
+template <typename Type> struct type_caster<std::valarray<Type>>
+ : array_caster<std::valarray<Type>, Type, true> { };
+
+template <typename Key, typename Compare, typename Alloc> struct type_caster<std::set<Key, Compare, Alloc>>
+  : set_caster<std::set<Key, Compare, Alloc>, Key> { };
+
+template <typename Key, typename Hash, typename Equal, typename Alloc> struct type_caster<std::unordered_set<Key, Hash, Equal, Alloc>>
+  : set_caster<std::unordered_set<Key, Hash, Equal, Alloc>, Key> { };
+
+template <typename Key, typename Value, typename Compare, typename Alloc> struct type_caster<std::map<Key, Value, Compare, Alloc>>
+  : map_caster<std::map<Key, Value, Compare, Alloc>, Key, Value> { };
+
+template <typename Key, typename Value, typename Hash, typename Equal, typename Alloc> struct type_caster<std::unordered_map<Key, Value, Hash, Equal, Alloc>>
+  : map_caster<std::unordered_map<Key, Value, Hash, Equal, Alloc>, Key, Value> { };
+
+// This type caster is intended to be used for std::optional and std::experimental::optional
+template<typename T> struct optional_caster {
+    using value_conv = make_caster<typename T::value_type>;
+
+    template <typename T_>
+    static handle cast(T_ &&src, return_value_policy policy, handle parent) {
+        if (!src)
+            return none().inc_ref();
+        return value_conv::cast(*std::forward<T_>(src), policy, parent);
+    }
+
+    bool load(handle src, bool convert) {
+        if (!src) {
+            return false;
+        } else if (src.is_none()) {
+            return true;  // default-constructed value is already empty
+        }
+        value_conv inner_caster;
+        if (!inner_caster.load(src, convert))
+            return false;
+
+        value.emplace(cast_op<typename T::value_type &&>(std::move(inner_caster)));
+        return true;
+    }
+
+    PYBIND11_TYPE_CASTER(T, _("Optional[") + value_conv::name + _("]"));
+};
+
+#if PYBIND11_HAS_OPTIONAL
+template<typename T> struct type_caster<std::optional<T>>
+    : public optional_caster<std::optional<T>> {};
+
+template<> struct type_caster<std::nullopt_t>
+    : public void_caster<std::nullopt_t> {};
+#endif
+
+#if PYBIND11_HAS_EXP_OPTIONAL
+template<typename T> struct type_caster<std::experimental::optional<T>>
+    : public optional_caster<std::experimental::optional<T>> {};
+
+template<> struct type_caster<std::experimental::nullopt_t>
+    : public void_caster<std::experimental::nullopt_t> {};
+#endif
+
+/// Visit a variant and cast any found type to Python
+struct variant_caster_visitor {
+    return_value_policy policy;
+    handle parent;
+
+    using result_type = handle; // required by boost::variant in C++11
+
+    template <typename T>
+    result_type operator()(T &&src) const {
+        return make_caster<T>::cast(std::forward<T>(src), policy, parent);
+    }
+};
+
+/// Helper class which abstracts away variant's `visit` function. `std::variant` and similar
+/// `namespace::variant` types which provide a `namespace::visit()` function are handled here
+/// automatically using argument-dependent lookup. Users can provide specializations for other
+/// variant-like classes, e.g. `boost::variant` and `boost::apply_visitor`.
+template <template<typename...> class Variant>
+struct visit_helper {
+    template <typename... Args>
+    static auto call(Args &&...args) -> decltype(visit(std::forward<Args>(args)...)) {
+        return visit(std::forward<Args>(args)...);
+    }
+};
+
+/// Generic variant caster
+template <typename Variant> struct variant_caster;
+
+template <template<typename...> class V, typename... Ts>
+struct variant_caster<V<Ts...>> {
+    static_assert(sizeof...(Ts) > 0, "Variant must consist of at least one alternative.");
+
+    template <typename U, typename... Us>
+    bool load_alternative(handle src, bool convert, type_list<U, Us...>) {
+        auto caster = make_caster<U>();
+        if (caster.load(src, convert)) {
+            value = cast_op<U>(caster);
+            return true;
+        }
+        return load_alternative(src, convert, type_list<Us...>{});
+    }
+
+    bool load_alternative(handle, bool, type_list<>) { return false; }
+
+    bool load(handle src, bool convert) {
+        // Do a first pass without conversions to improve constructor resolution.
+        // E.g. `py::int_(1).cast<variant<double, int>>()` needs to fill the `int`
+        // slot of the variant. Without two-pass loading `double` would be filled
+        // because it appears first and a conversion is possible.
+        if (convert && load_alternative(src, false, type_list<Ts...>{}))
+            return true;
+        return load_alternative(src, convert, type_list<Ts...>{});
+    }
+
+    template <typename Variant>
+    static handle cast(Variant &&src, return_value_policy policy, handle parent) {
+        return visit_helper<V>::call(variant_caster_visitor{policy, parent},
+                                     std::forward<Variant>(src));
+    }
+
+    using Type = V<Ts...>;
+    PYBIND11_TYPE_CASTER(Type, _("Union[") + detail::concat(make_caster<Ts>::name...) + _("]"));
+};
+
+#if PYBIND11_HAS_VARIANT
+template <typename... Ts>
+struct type_caster<std::variant<Ts...>> : variant_caster<std::variant<Ts...>> { };
+#endif
+NAMESPACE_END(detail)
+
+inline std::ostream &operator<<(std::ostream &os, const handle &obj) {
+    os << (std::string) str(obj);
+    return os;
+}
+
+NAMESPACE_END(PYBIND11_NAMESPACE)
+
+#if defined(_MSC_VER)
+#pragma warning(pop)
+#endif

dlib/external/pybind11/include/pybind11/stl_bind.h

+/*
+    pybind11/std_bind.h: Binding generators for STL data types
+
+    Copyright (c) 2016 Sergey Lyskov and Wenzel Jakob
+
+    All rights reserved. Use of this source code is governed by a
+    BSD-style license that can be found in the LICENSE file.
+*/
+
+#pragma once
+
+#include "detail/common.h"
+#include "operators.h"
+
+#include <algorithm>
+#include <sstream>
+
+NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
+NAMESPACE_BEGIN(detail)
+
+/* SFINAE helper class used by 'is_comparable */
+template <typename T>  struct container_traits {
+    template <typename T2> static std::true_type test_comparable(decltype(std::declval<const T2 &>() == std::declval<const T2 &>())*);
+    template <typename T2> static std::false_type test_comparable(...);
+    template <typename T2> static std::true_type test_value(typename T2::value_type *);
+    template <typename T2> static std::false_type test_value(...);
+    template <typename T2> static std::true_type test_pair(typename T2::first_type *, typename T2::second_type *);
+    template <typename T2> static std::false_type test_pair(...);
+
+    static constexpr const bool is_comparable = std::is_same<std::true_type, decltype(test_comparable<T>(nullptr))>::value;
+    static constexpr const bool is_pair = std::is_same<std::true_type, decltype(test_pair<T>(nullptr, nullptr))>::value;
+    static constexpr const bool is_vector = std::is_same<std::true_type, decltype(test_value<T>(nullptr))>::value;
+    static constexpr const bool is_element = !is_pair && !is_vector;
+};
+
+/* Default: is_comparable -> std::false_type */
+template <typename T, typename SFINAE = void>
+struct is_comparable : std::false_type { };
+
+/* For non-map data structures, check whether operator== can be instantiated */
+template <typename T>
+struct is_comparable<
+    T, enable_if_t<container_traits<T>::is_element &&
+                   container_traits<T>::is_comparable>>
+    : std::true_type { };
+
+/* For a vector/map data structure, recursively check the value type (which is std::pair for maps) */
+template <typename T>
+struct is_comparable<T, enable_if_t<container_traits<T>::is_vector>> {
+    static constexpr const bool value =
+        is_comparable<typename T::value_type>::value;
+};
+
+/* For pairs, recursively check the two data types */
+template <typename T>
+struct is_comparable<T, enable_if_t<container_traits<T>::is_pair>> {
+    static constexpr const bool value =
+        is_comparable<typename T::first_type>::value &&
+        is_comparable<typename T::second_type>::value;
+};
+
+/* Fallback functions */
+template <typename, typename, typename... Args> void vector_if_copy_constructible(const Args &...) { }
+template <typename, typename, typename... Args> void vector_if_equal_operator(const Args &...) { }
+template <typename, typename, typename... Args> void vector_if_insertion_operator(const Args &...) { }
+template <typename, typename, typename... Args> void vector_modifiers(const Args &...) { }
+
+template<typename Vector, typename Class_>
+void vector_if_copy_constructible(enable_if_t<is_copy_constructible<Vector>::value, Class_> &cl) {
+    cl.def(init<const Vector &>(), "Copy constructor");
+}
+
+template<typename Vector, typename Class_>
+void vector_if_equal_operator(enable_if_t<is_comparable<Vector>::value, Class_> &cl) {
+    using T = typename Vector::value_type;
+
+    cl.def(self == self);
+    cl.def(self != self);
+
+    cl.def("count",
+        [](const Vector &v, const T &x) {
+            return std::count(v.begin(), v.end(), x);
+        },
+        arg("x"),
+        "Return the number of times ``x`` appears in the list"
+    );
+
+    cl.def("remove", [](Vector &v, const T &x) {
+            auto p = std::find(v.begin(), v.end(), x);
+            if (p != v.end())
+                v.erase(p);
+            else
+                throw value_error();
+        },
+        arg("x"),
+        "Remove the first item from the list whose value is x. "
+        "It is an error if there is no such item."
+    );
+
+    cl.def("__contains__",
+        [](const Vector &v, const T &x) {
+            return std::find(v.begin(), v.end(), x) != v.end();
+        },
+        arg("x"),
+        "Return true the container contains ``x``"
+    );
+}
+
+// Vector modifiers -- requires a copyable vector_type:
+// (Technically, some of these (pop and __delitem__) don't actually require copyability, but it seems
+// silly to allow deletion but not insertion, so include them here too.)
+template <typename Vector, typename Class_>
+void vector_modifiers(enable_if_t<is_copy_constructible<typename Vector::value_type>::value, Class_> &cl) {
+    using T = typename Vector::value_type;
+    using SizeType = typename Vector::size_type;
+    using DiffType = typename Vector::difference_type;
+
+    cl.def("append",
+           [](Vector &v, const T &value) { v.push_back(value); },
+           arg("x"),
+           "Add an item to the end of the list");
+
+    cl.def(init([](iterable it) {
+        auto v = std::unique_ptr<Vector>(new Vector());
+        v->reserve(len(it));
+        for (handle h : it)
+           v->push_back(h.cast<T>());
+        return v.release();
+    }));
+
+    cl.def("extend",
+       [](Vector &v, const Vector &src) {
+           v.insert(v.end(), src.begin(), src.end());
+       },
+       arg("L"),
+       "Extend the list by appending all the items in the given list"
+    );
+
+    cl.def("insert",
+        [](Vector &v, SizeType i, const T &x) {
+            if (i > v.size())
+                throw index_error();
+            v.insert(v.begin() + (DiffType) i, x);
+        },
+        arg("i") , arg("x"),
+        "Insert an item at a given position."
+    );
+
+    cl.def("pop",
+        [](Vector &v) {
+            if (v.empty())
+                throw index_error();
+            T t = v.back();
+            v.pop_back();
+            return t;
+        },
+        "Remove and return the last item"
+    );
+
+    cl.def("pop",
+        [](Vector &v, SizeType i) {
+            if (i >= v.size())
+                throw index_error();
+            T t = v[i];
+            v.erase(v.begin() + (DiffType) i);
+            return t;
+        },
+        arg("i"),
+        "Remove and return the item at index ``i``"
+    );
+
+    cl.def("__setitem__",
+        [](Vector &v, SizeType i, const T &t) {
+            if (i >= v.size())
+                throw index_error();
+            v[i] = t;
+        }
+    );
+
+    /// Slicing protocol
+    cl.def("__getitem__",
+        [](const Vector &v, slice slice) -> Vector * {
+            size_t start, stop, step, slicelength;
+
+            if (!slice.compute(v.size(), &start, &stop, &step, &slicelength))
+                throw error_already_set();
+
+            Vector *seq = new Vector();
+            seq->reserve((size_t) slicelength);
+
+            for (size_t i=0; i<slicelength; ++i) {
+                seq->push_back(v[start]);
+                start += step;
+            }
+            return seq;
+        },
+        arg("s"),
+        "Retrieve list elements using a slice object"
+    );
+
+    cl.def("__setitem__",
+        [](Vector &v, slice slice,  const Vector &value) {
+            size_t start, stop, step, slicelength;
+            if (!slice.compute(v.size(), &start, &stop, &step, &slicelength))
+                throw error_already_set();
+
+            if (slicelength != value.size())
+                throw std::runtime_error("Left and right hand size of slice assignment have different sizes!");
+
+            for (size_t i=0; i<slicelength; ++i) {
+                v[start] = value[i];
+                start += step;
+            }
+        },
+        "Assign list elements using a slice object"
+    );
+
+    cl.def("__delitem__",
+        [](Vector &v, SizeType i) {
+            if (i >= v.size())
+                throw index_error();
+            v.erase(v.begin() + DiffType(i));
+        },
+        "Delete the list elements at index ``i``"
+    );
+
+    cl.def("__delitem__",
+        [](Vector &v, slice slice) {
+            size_t start, stop, step, slicelength;
+
+            if (!slice.compute(v.size(), &start, &stop, &step, &slicelength))
+                throw error_already_set();
+
+            if (step == 1 && false) {
+                v.erase(v.begin() + (DiffType) start, v.begin() + DiffType(start + slicelength));
+            } else {
+                for (size_t i = 0; i < slicelength; ++i) {
+                    v.erase(v.begin() + DiffType(start));
+                    start += step - 1;
+                }
+            }
+        },
+        "Delete list elements using a slice object"
+    );
+
+}
+
+// If the type has an operator[] that doesn't return a reference (most notably std::vector<bool>),
+// we have to access by copying; otherwise we return by reference.
+template <typename Vector> using vector_needs_copy = negation<
+    std::is_same<decltype(std::declval<Vector>()[typename Vector::size_type()]), typename Vector::value_type &>>;
+
+// The usual case: access and iterate by reference
+template <typename Vector, typename Class_>
+void vector_accessor(enable_if_t<!vector_needs_copy<Vector>::value, Class_> &cl) {
+    using T = typename Vector::value_type;
+    using SizeType = typename Vector::size_type;
+    using ItType   = typename Vector::iterator;
+
+    cl.def("__getitem__",
+        [](Vector &v, SizeType i) -> T & {
+            if (i >= v.size())
+                throw index_error();
+            return v[i];
+        },
+        return_value_policy::reference_internal // ref + keepalive
+    );
+
+    cl.def("__iter__",
+           [](Vector &v) {
+               return make_iterator<
+                   return_value_policy::reference_internal, ItType, ItType, T&>(
+                   v.begin(), v.end());
+           },
+           keep_alive<0, 1>() /* Essential: keep list alive while iterator exists */
+    );
+}
+
+// The case for special objects, like std::vector<bool>, that have to be returned-by-copy:
+template <typename Vector, typename Class_>
+void vector_accessor(enable_if_t<vector_needs_copy<Vector>::value, Class_> &cl) {
+    using T = typename Vector::value_type;
+    using SizeType = typename Vector::size_type;
+    using ItType   = typename Vector::iterator;
+    cl.def("__getitem__",
+        [](const Vector &v, SizeType i) -> T {
+            if (i >= v.size())
+                throw index_error();
+            return v[i];
+        }
+    );
+
+    cl.def("__iter__",
+           [](Vector &v) {
+               return make_iterator<
+                   return_value_policy::copy, ItType, ItType, T>(
+                   v.begin(), v.end());
+           },
+           keep_alive<0, 1>() /* Essential: keep list alive while iterator exists */
+    );
+}
+
+template <typename Vector, typename Class_> auto vector_if_insertion_operator(Class_ &cl, std::string const &name)
+    -> decltype(std::declval<std::ostream&>() << std::declval<typename Vector::value_type>(), void()) {
+    using size_type = typename Vector::size_type;
+
+    cl.def("__repr__",
+           [name](Vector &v) {
+            std::ostringstream s;
+            s << name << '[';
+            for (size_type i=0; i < v.size(); ++i) {
+                s << v[i];
+                if (i != v.size() - 1)
+                    s << ", ";
+            }
+            s << ']';
+            return s.str();
+        },
+        "Return the canonical string representation of this list."
+    );
+}
+
+// Provide the buffer interface for vectors if we have data() and we have a format for it
+// GCC seems to have "void std::vector<bool>::data()" - doing SFINAE on the existence of data() is insufficient, we need to check it returns an appropriate pointer
+template <typename Vector, typename = void>
+struct vector_has_data_and_format : std::false_type {};
+template <typename Vector>
+struct vector_has_data_and_format<Vector, enable_if_t<std::is_same<decltype(format_descriptor<typename Vector::value_type>::format(), std::declval<Vector>().data()), typename Vector::value_type*>::value>> : std::true_type {};
+
+// Add the buffer interface to a vector
+template <typename Vector, typename Class_, typename... Args>
+enable_if_t<detail::any_of<std::is_same<Args, buffer_protocol>...>::value>
+vector_buffer(Class_& cl) {
+    using T = typename Vector::value_type;
+
+    static_assert(vector_has_data_and_format<Vector>::value, "There is not an appropriate format descriptor for this vector");
+
+    // numpy.h declares this for arbitrary types, but it may raise an exception and crash hard at runtime if PYBIND11_NUMPY_DTYPE hasn't been called, so check here
+    format_descriptor<T>::format();
+
+    cl.def_buffer([](Vector& v) -> buffer_info {
+        return buffer_info(v.data(), static_cast<ssize_t>(sizeof(T)), format_descriptor<T>::format(), 1, {v.size()}, {sizeof(T)});
+    });
+
+    cl.def(init([](buffer buf) {
+        auto info = buf.request();
+        if (info.ndim != 1 || info.strides[0] % static_cast<ssize_t>(sizeof(T)))
+            throw type_error("Only valid 1D buffers can be copied to a vector");
+        if (!detail::compare_buffer_info<T>::compare(info) || (ssize_t) sizeof(T) != info.itemsize)
+            throw type_error("Format mismatch (Python: " + info.format + " C++: " + format_descriptor<T>::format() + ")");
+
+        auto vec = std::unique_ptr<Vector>(new Vector());
+        vec->reserve((size_t) info.shape[0]);
+        T *p = static_cast<T*>(info.ptr);
+        ssize_t step = info.strides[0] / static_cast<ssize_t>(sizeof(T));
+        T *end = p + info.shape[0] * step;
+        for (; p != end; p += step)
+            vec->push_back(*p);
+        return vec.release();
+    }));
+
+    return;
+}
+
+template <typename Vector, typename Class_, typename... Args>
+enable_if_t<!detail::any_of<std::is_same<Args, buffer_protocol>...>::value> vector_buffer(Class_&) {}
+
+NAMESPACE_END(detail)
+
+//
+// std::vector
+//
+template <typename Vector, typename holder_type = std::unique_ptr<Vector>, typename... Args>
+class_<Vector, holder_type> bind_vector(handle scope, std::string const &name, Args&&... args) {
+    using Class_ = class_<Vector, holder_type>;
+
+    // If the value_type is unregistered (e.g. a converting type) or is itself registered
+    // module-local then make the vector binding module-local as well:
+    using vtype = typename Vector::value_type;
+    auto vtype_info = detail::get_type_info(typeid(vtype));
+    bool local = !vtype_info || vtype_info->module_local;
+
+    Class_ cl(scope, name.c_str(), pybind11::module_local(local), std::forward<Args>(args)...);
+
+    // Declare the buffer interface if a buffer_protocol() is passed in
+    detail::vector_buffer<Vector, Class_, Args...>(cl);
+
+    cl.def(init<>());
+
+    // Register copy constructor (if possible)
+    detail::vector_if_copy_constructible<Vector, Class_>(cl);
+
+    // Register comparison-related operators and functions (if possible)
+    detail::vector_if_equal_operator<Vector, Class_>(cl);
+
+    // Register stream insertion operator (if possible)
+    detail::vector_if_insertion_operator<Vector, Class_>(cl, name);
+
+    // Modifiers require copyable vector value type
+    detail::vector_modifiers<Vector, Class_>(cl);
+
+    // Accessor and iterator; return by value if copyable, otherwise we return by ref + keep-alive
+    detail::vector_accessor<Vector, Class_>(cl);
+
+    cl.def("__bool__",
+        [](const Vector &v) -> bool {
+            return !v.empty();
+        },
+        "Check whether the list is nonempty"
+    );
+
+    cl.def("__len__", &Vector::size);
+
+
+
+
+#if 0
+    // C++ style functions deprecated, leaving it here as an example
+    cl.def(init<size_type>());
+
+    cl.def("resize",
+         (void (Vector::*) (size_type count)) & Vector::resize,
+         "changes the number of elements stored");
+
+    cl.def("erase",
+        [](Vector &v, SizeType i) {
+        if (i >= v.size())
+            throw index_error();
+        v.erase(v.begin() + i);
+    }, "erases element at index ``i``");
+
+    cl.def("empty",         &Vector::empty,         "checks whether the container is empty");
+    cl.def("size",          &Vector::size,          "returns the number of elements");
+    cl.def("push_back", (void (Vector::*)(const T&)) &Vector::push_back, "adds an element to the end");
+    cl.def("pop_back",                               &Vector::pop_back, "removes the last element");
+
+    cl.def("max_size",      &Vector::max_size,      "returns the maximum possible number of elements");
+    cl.def("reserve",       &Vector::reserve,       "reserves storage");
+    cl.def("capacity",      &Vector::capacity,      "returns the number of elements that can be held in currently allocated storage");
+    cl.def("shrink_to_fit", &Vector::shrink_to_fit, "reduces memory usage by freeing unused memory");
+
+    cl.def("clear", &Vector::clear, "clears the contents");
+    cl.def("swap",   &Vector::swap, "swaps the contents");
+
+    cl.def("front", [](Vector &v) {
+        if (v.size()) return v.front();
+        else throw index_error();
+    }, "access the first element");
+
+    cl.def("back", [](Vector &v) {
+        if (v.size()) return v.back();
+        else throw index_error();
+    }, "access the last element ");
+
+#endif
+
+    return cl;
+}
+
+
+
+//
+// std::map, std::unordered_map
+//
+
+NAMESPACE_BEGIN(detail)
+
+/* Fallback functions */
+template <typename, typename, typename... Args> void map_if_insertion_operator(const Args &...) { }
+template <typename, typename, typename... Args> void map_assignment(const Args &...) { }
+
+// Map assignment when copy-assignable: just copy the value
+template <typename Map, typename Class_>
+void map_assignment(enable_if_t<std::is_copy_assignable<typename Map::mapped_type>::value, Class_> &cl) {
+    using KeyType = typename Map::key_type;
+    using MappedType = typename Map::mapped_type;
+
+    cl.def("__setitem__",
+           [](Map &m, const KeyType &k, const MappedType &v) {
+               auto it = m.find(k);
+               if (it != m.end()) it->second = v;
+               else m.emplace(k, v);
+           }
+    );
+}
+
+// Not copy-assignable, but still copy-constructible: we can update the value by erasing and reinserting
+template<typename Map, typename Class_>
+void map_assignment(enable_if_t<
+        !std::is_copy_assignable<typename Map::mapped_type>::value &&
+        is_copy_constructible<typename Map::mapped_type>::value,
+        Class_> &cl) {
+    using KeyType = typename Map::key_type;
+    using MappedType = typename Map::mapped_type;
+
+    cl.def("__setitem__",
+           [](Map &m, const KeyType &k, const MappedType &v) {
+               // We can't use m[k] = v; because value type might not be default constructable
+               auto r = m.emplace(k, v);
+               if (!r.second) {
+                   // value type is not copy assignable so the only way to insert it is to erase it first...
+                   m.erase(r.first);
+                   m.emplace(k, v);
+               }
+           }
+    );
+}
+
+
+template <typename Map, typename Class_> auto map_if_insertion_operator(Class_ &cl, std::string const &name)
+-> decltype(std::declval<std::ostream&>() << std::declval<typename Map::key_type>() << std::declval<typename Map::mapped_type>(), void()) {
+
+    cl.def("__repr__",
+           [name](Map &m) {
+            std::ostringstream s;
+            s << name << '{';
+            bool f = false;
+            for (auto const &kv : m) {
+                if (f)
+                    s << ", ";
+                s << kv.first << ": " << kv.second;
+                f = true;
+            }
+            s << '}';
+            return s.str();
+        },
+        "Return the canonical string representation of this map."
+    );
+}
+
+
+NAMESPACE_END(detail)
+
+template <typename Map, typename holder_type = std::unique_ptr<Map>, typename... Args>
+class_<Map, holder_type> bind_map(handle scope, const std::string &name, Args&&... args) {
+    using KeyType = typename Map::key_type;
+    using MappedType = typename Map::mapped_type;
+    using Class_ = class_<Map, holder_type>;
+
+    // If either type is a non-module-local bound type then make the map binding non-local as well;
+    // otherwise (e.g. both types are either module-local or converting) the map will be
+    // module-local.
+    auto tinfo = detail::get_type_info(typeid(MappedType));
+    bool local = !tinfo || tinfo->module_local;
+    if (local) {
+        tinfo = detail::get_type_info(typeid(KeyType));
+        local = !tinfo || tinfo->module_local;
+    }
+
+    Class_ cl(scope, name.c_str(), pybind11::module_local(local), std::forward<Args>(args)...);
+
+    cl.def(init<>());
+
+    // Register stream insertion operator (if possible)
+    detail::map_if_insertion_operator<Map, Class_>(cl, name);
+
+    cl.def("__bool__",
+        [](const Map &m) -> bool { return !m.empty(); },
+        "Check whether the map is nonempty"
+    );
+
+    cl.def("__iter__",
+           [](Map &m) { return make_key_iterator(m.begin(), m.end()); },
+           keep_alive<0, 1>() /* Essential: keep list alive while iterator exists */
+    );
+
+    cl.def("items",
+           [](Map &m) { return make_iterator(m.begin(), m.end()); },
+           keep_alive<0, 1>() /* Essential: keep list alive while iterator exists */
+    );
+
+    cl.def("__getitem__",
+        [](Map &m, const KeyType &k) -> MappedType & {
+            auto it = m.find(k);
+            if (it == m.end())
+              throw key_error();
+           return it->second;
+        },
+        return_value_policy::reference_internal // ref + keepalive
+    );
+
+    // Assignment provided only if the type is copyable
+    detail::map_assignment<Map, Class_>(cl);
+
+    cl.def("__delitem__",
+           [](Map &m, const KeyType &k) {
+               auto it = m.find(k);
+               if (it == m.end())
+                   throw key_error();
+               return m.erase(it);
+           }
+    );
+
+    cl.def("__len__", &Map::size);
+
+    return cl;
+}
+
+NAMESPACE_END(PYBIND11_NAMESPACE)

dlib/external/pybind11/tools/FindCatch.cmake

+# - Find the Catch test framework or download it (single header)
+#
+# This is a quick module for internal use. It assumes that Catch is
+# REQUIRED and that a minimum version is provided (not EXACT). If
+# a suitable version isn't found locally, the single header file
+# will be downloaded and placed in the build dir: PROJECT_BINARY_DIR.
+#
+# This code sets the following variables:
+#  CATCH_INCLUDE_DIR      - path to catch.hpp
+#  CATCH_VERSION          - version number
+
+if(NOT Catch_FIND_VERSION)
+  message(FATAL_ERROR "A version number must be specified.")
+elseif(Catch_FIND_REQUIRED)
+  message(FATAL_ERROR "This module assumes Catch is not required.")
+elseif(Catch_FIND_VERSION_EXACT)
+  message(FATAL_ERROR "Exact version numbers are not supported, only minimum.")
+endif()
+
+# Extract the version number from catch.hpp
+function(_get_catch_version)
+  file(STRINGS "${CATCH_INCLUDE_DIR}/catch.hpp" version_line REGEX "Catch v.*" LIMIT_COUNT 1)
+  if(version_line MATCHES "Catch v([0-9]+)\\.([0-9]+)\\.([0-9]+)")
+    set(CATCH_VERSION "${CMAKE_MATCH_1}.${CMAKE_MATCH_2}.${CMAKE_MATCH_3}" PARENT_SCOPE)
+  endif()
+endfunction()
+
+# Download the single-header version of Catch
+function(_download_catch version destination_dir)
+  message(STATUS "Downloading catch v${version}...")
+  set(url https://github.com/philsquared/Catch/releases/download/v${version}/catch.hpp)
+  file(DOWNLOAD ${url} "${destination_dir}/catch.hpp" STATUS status)
+  list(GET status 0 error)
+  if(error)
+    message(FATAL_ERROR "Could not download ${url}")
+  endif()
+  set(CATCH_INCLUDE_DIR "${destination_dir}" CACHE INTERNAL "")
+endfunction()
+
+# Look for catch locally
+find_path(CATCH_INCLUDE_DIR NAMES catch.hpp PATH_SUFFIXES catch)
+if(CATCH_INCLUDE_DIR)
+  _get_catch_version()
+endif()
+
+# Download the header if it wasn't found or if it's outdated
+if(NOT CATCH_VERSION OR CATCH_VERSION VERSION_LESS ${Catch_FIND_VERSION})
+  if(DOWNLOAD_CATCH)
+    _download_catch(${Catch_FIND_VERSION} "${PROJECT_BINARY_DIR}/catch/")
+    _get_catch_version()
+  else()
+    set(CATCH_FOUND FALSE)
+    return()
+  endif()
+endif()
+
+set(CATCH_FOUND TRUE)

dlib/external/pybind11/tools/FindEigen3.cmake

+# - Try to find Eigen3 lib
+#
+# This module supports requiring a minimum version, e.g. you can do
+#   find_package(Eigen3 3.1.2)
+# to require version 3.1.2 or newer of Eigen3.
+#
+# Once done this will define
+#
+#  EIGEN3_FOUND - system has eigen lib with correct version
+#  EIGEN3_INCLUDE_DIR - the eigen include directory
+#  EIGEN3_VERSION - eigen version
+
+# Copyright (c) 2006, 2007 Montel Laurent, <montel@kde.org>
+# Copyright (c) 2008, 2009 Gael Guennebaud, <g.gael@free.fr>
+# Copyright (c) 2009 Benoit Jacob <jacob.benoit.1@gmail.com>
+# Redistribution and use is allowed according to the terms of the 2-clause BSD license.
+
+if(NOT Eigen3_FIND_VERSION)
+  if(NOT Eigen3_FIND_VERSION_MAJOR)
+    set(Eigen3_FIND_VERSION_MAJOR 2)
+  endif(NOT Eigen3_FIND_VERSION_MAJOR)
+  if(NOT Eigen3_FIND_VERSION_MINOR)
+    set(Eigen3_FIND_VERSION_MINOR 91)
+  endif(NOT Eigen3_FIND_VERSION_MINOR)
+  if(NOT Eigen3_FIND_VERSION_PATCH)
+    set(Eigen3_FIND_VERSION_PATCH 0)
+  endif(NOT Eigen3_FIND_VERSION_PATCH)
+
+  set(Eigen3_FIND_VERSION "${Eigen3_FIND_VERSION_MAJOR}.${Eigen3_FIND_VERSION_MINOR}.${Eigen3_FIND_VERSION_PATCH}")
+endif(NOT Eigen3_FIND_VERSION)
+
+macro(_eigen3_check_version)
+  file(READ "${EIGEN3_INCLUDE_DIR}/Eigen/src/Core/util/Macros.h" _eigen3_version_header)
+
+  string(REGEX MATCH "define[ \t]+EIGEN_WORLD_VERSION[ \t]+([0-9]+)" _eigen3_world_version_match "${_eigen3_version_header}")
+  set(EIGEN3_WORLD_VERSION "${CMAKE_MATCH_1}")
+  string(REGEX MATCH "define[ \t]+EIGEN_MAJOR_VERSION[ \t]+([0-9]+)" _eigen3_major_version_match "${_eigen3_version_header}")
+  set(EIGEN3_MAJOR_VERSION "${CMAKE_MATCH_1}")
+  string(REGEX MATCH "define[ \t]+EIGEN_MINOR_VERSION[ \t]+([0-9]+)" _eigen3_minor_version_match "${_eigen3_version_header}")
+  set(EIGEN3_MINOR_VERSION "${CMAKE_MATCH_1}")
+
+  set(EIGEN3_VERSION ${EIGEN3_WORLD_VERSION}.${EIGEN3_MAJOR_VERSION}.${EIGEN3_MINOR_VERSION})
+  if(${EIGEN3_VERSION} VERSION_LESS ${Eigen3_FIND_VERSION})
+    set(EIGEN3_VERSION_OK FALSE)
+  else(${EIGEN3_VERSION} VERSION_LESS ${Eigen3_FIND_VERSION})
+    set(EIGEN3_VERSION_OK TRUE)
+  endif(${EIGEN3_VERSION} VERSION_LESS ${Eigen3_FIND_VERSION})
+
+  if(NOT EIGEN3_VERSION_OK)
+
+    message(STATUS "Eigen3 version ${EIGEN3_VERSION} found in ${EIGEN3_INCLUDE_DIR}, "
+                   "but at least version ${Eigen3_FIND_VERSION} is required")
+  endif(NOT EIGEN3_VERSION_OK)
+endmacro(_eigen3_check_version)
+
+if (EIGEN3_INCLUDE_DIR)
+
+  # in cache already
+  _eigen3_check_version()
+  set(EIGEN3_FOUND ${EIGEN3_VERSION_OK})
+
+else (EIGEN3_INCLUDE_DIR)
+
+  find_path(EIGEN3_INCLUDE_DIR NAMES signature_of_eigen3_matrix_library
+      PATHS
+      ${CMAKE_INSTALL_PREFIX}/include
+      ${KDE4_INCLUDE_DIR}
+      PATH_SUFFIXES eigen3 eigen
+    )
+
+  if(EIGEN3_INCLUDE_DIR)
+    _eigen3_check_version()
+  endif(EIGEN3_INCLUDE_DIR)
+
+  include(FindPackageHandleStandardArgs)
+  find_package_handle_standard_args(Eigen3 DEFAULT_MSG EIGEN3_INCLUDE_DIR EIGEN3_VERSION_OK)
+
+  mark_as_advanced(EIGEN3_INCLUDE_DIR)
+
+endif(EIGEN3_INCLUDE_DIR)
+

dlib/external/pybind11/tools/FindPythonLibsNew.cmake

+# - Find python libraries
+# This module finds the libraries corresponding to the Python interpeter
+# FindPythonInterp provides.
+# This code sets the following variables:
+#
+#  PYTHONLIBS_FOUND           - have the Python libs been found
+#  PYTHON_PREFIX              - path to the Python installation
+#  PYTHON_LIBRARIES           - path to the python library
+#  PYTHON_INCLUDE_DIRS        - path to where Python.h is found
+#  PYTHON_MODULE_EXTENSION    - lib extension, e.g. '.so' or '.pyd'
+#  PYTHON_MODULE_PREFIX       - lib name prefix: usually an empty string
+#  PYTHON_SITE_PACKAGES       - path to installation site-packages
+#  PYTHON_IS_DEBUG            - whether the Python interpreter is a debug build
+#
+# Thanks to talljimbo for the patch adding the 'LDVERSION' config
+# variable usage.
+
+#=============================================================================
+# Copyright 2001-2009 Kitware, Inc.
+# Copyright 2012 Continuum Analytics, Inc.
+#
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions
+# are met:
+#
+# * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#
+# * Redistributions in binary form must reproduce the above copyright
+# notice, this list of conditions and the following disclaimer in the
+# documentation and/or other materials provided with the distribution.
+#
+# * Neither the names of Kitware, Inc., the Insight Software Consortium,
+# nor the names of their contributors may be used to endorse or promote
+# products derived from this software without specific prior written
+# permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# # A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#=============================================================================
+
+# Checking for the extension makes sure that `LibsNew` was found and not just `Libs`.
+if(PYTHONLIBS_FOUND AND PYTHON_MODULE_EXTENSION)
+    return()
+endif()
+
+# Use the Python interpreter to find the libs.
+if(PythonLibsNew_FIND_REQUIRED)
+    find_package(PythonInterp ${PythonLibsNew_FIND_VERSION} REQUIRED)
+else()
+    find_package(PythonInterp ${PythonLibsNew_FIND_VERSION})
+endif()
+
+if(NOT PYTHONINTERP_FOUND)
+    set(PYTHONLIBS_FOUND FALSE)
+    return()
+endif()
+
+# According to http://stackoverflow.com/questions/646518/python-how-to-detect-debug-interpreter
+# testing whether sys has the gettotalrefcount function is a reliable, cross-platform
+# way to detect a CPython debug interpreter.
+#
+# The library suffix is from the config var LDVERSION sometimes, otherwise
+# VERSION. VERSION will typically be like "2.7" on unix, and "27" on windows.
+execute_process(COMMAND "${PYTHON_EXECUTABLE}" "-c"
+    "from distutils import sysconfig as s;import sys;import struct;
+print('.'.join(str(v) for v in sys.version_info));
+print(sys.prefix);
+print(s.get_python_inc(plat_specific=True));
+print(s.get_python_lib(plat_specific=True));
+print(s.get_config_var('SO'));
+print(hasattr(sys, 'gettotalrefcount')+0);
+print(struct.calcsize('@P'));
+print(s.get_config_var('LDVERSION') or s.get_config_var('VERSION'));
+print(s.get_config_var('LIBDIR') or '');
+print(s.get_config_var('MULTIARCH') or '');
+"
+    RESULT_VARIABLE _PYTHON_SUCCESS
+    OUTPUT_VARIABLE _PYTHON_VALUES
+    ERROR_VARIABLE _PYTHON_ERROR_VALUE)
+
+if(NOT _PYTHON_SUCCESS MATCHES 0)
+    if(PythonLibsNew_FIND_REQUIRED)
+        message(FATAL_ERROR
+            "Python config failure:\n${_PYTHON_ERROR_VALUE}")
+    endif()
+    set(PYTHONLIBS_FOUND FALSE)
+    return()
+endif()
+
+# Convert the process output into a list
+string(REGEX REPLACE ";" "\\\\;" _PYTHON_VALUES ${_PYTHON_VALUES})
+string(REGEX REPLACE "\n" ";" _PYTHON_VALUES ${_PYTHON_VALUES})
+list(GET _PYTHON_VALUES 0 _PYTHON_VERSION_LIST)
+list(GET _PYTHON_VALUES 1 PYTHON_PREFIX)
+list(GET _PYTHON_VALUES 2 PYTHON_INCLUDE_DIR)
+list(GET _PYTHON_VALUES 3 PYTHON_SITE_PACKAGES)
+list(GET _PYTHON_VALUES 4 PYTHON_MODULE_EXTENSION)
+list(GET _PYTHON_VALUES 5 PYTHON_IS_DEBUG)
+list(GET _PYTHON_VALUES 6 PYTHON_SIZEOF_VOID_P)
+list(GET _PYTHON_VALUES 7 PYTHON_LIBRARY_SUFFIX)
+list(GET _PYTHON_VALUES 8 PYTHON_LIBDIR)
+list(GET _PYTHON_VALUES 9 PYTHON_MULTIARCH)
+
+# Make sure the Python has the same pointer-size as the chosen compiler
+# Skip if CMAKE_SIZEOF_VOID_P is not defined
+if(CMAKE_SIZEOF_VOID_P AND (NOT "${PYTHON_SIZEOF_VOID_P}" STREQUAL "${CMAKE_SIZEOF_VOID_P}"))
+    if(PythonLibsNew_FIND_REQUIRED)
+        math(EXPR _PYTHON_BITS "${PYTHON_SIZEOF_VOID_P} * 8")
+        math(EXPR _CMAKE_BITS "${CMAKE_SIZEOF_VOID_P} * 8")
+        message(FATAL_ERROR
+            "Python config failure: Python is ${_PYTHON_BITS}-bit, "
+            "chosen compiler is  ${_CMAKE_BITS}-bit")
+    endif()
+    set(PYTHONLIBS_FOUND FALSE)
+    return()
+endif()
+
+# The built-in FindPython didn't always give the version numbers
+string(REGEX REPLACE "\\." ";" _PYTHON_VERSION_LIST ${_PYTHON_VERSION_LIST})
+list(GET _PYTHON_VERSION_LIST 0 PYTHON_VERSION_MAJOR)
+list(GET _PYTHON_VERSION_LIST 1 PYTHON_VERSION_MINOR)
+list(GET _PYTHON_VERSION_LIST 2 PYTHON_VERSION_PATCH)
+
+# Make sure all directory separators are '/'
+string(REGEX REPLACE "\\\\" "/" PYTHON_PREFIX ${PYTHON_PREFIX})
+string(REGEX REPLACE "\\\\" "/" PYTHON_INCLUDE_DIR ${PYTHON_INCLUDE_DIR})
+string(REGEX REPLACE "\\\\" "/" PYTHON_SITE_PACKAGES ${PYTHON_SITE_PACKAGES})
+
+if(CMAKE_HOST_WIN32)
+    set(PYTHON_LIBRARY
+        "${PYTHON_PREFIX}/libs/Python${PYTHON_LIBRARY_SUFFIX}.lib")
+
+    # when run in a venv, PYTHON_PREFIX points to it. But the libraries remain in the
+    # original python installation. They may be found relative to PYTHON_INCLUDE_DIR.
+    if(NOT EXISTS "${PYTHON_LIBRARY}")
+        get_filename_component(_PYTHON_ROOT ${PYTHON_INCLUDE_DIR} DIRECTORY)
+        set(PYTHON_LIBRARY
+            "${_PYTHON_ROOT}/libs/Python${PYTHON_LIBRARY_SUFFIX}.lib")
+    endif()
+
+    # raise an error if the python libs are still not found.
+    if(NOT EXISTS "${PYTHON_LIBRARY}")
+        message(FATAL_ERROR "Python libraries not found")
+    endif()
+
+else()
+    if(PYTHON_MULTIARCH)
+        set(_PYTHON_LIBS_SEARCH "${PYTHON_LIBDIR}/${PYTHON_MULTIARCH}" "${PYTHON_LIBDIR}")
+    else()
+        set(_PYTHON_LIBS_SEARCH "${PYTHON_LIBDIR}")
+    endif()
+    #message(STATUS "Searching for Python libs in ${_PYTHON_LIBS_SEARCH}")
+    # Probably this needs to be more involved. It would be nice if the config
+    # information the python interpreter itself gave us were more complete.
+    find_library(PYTHON_LIBRARY
+        NAMES "python${PYTHON_LIBRARY_SUFFIX}"
+        PATHS ${_PYTHON_LIBS_SEARCH}
+        NO_DEFAULT_PATH)
+
+    # If all else fails, just set the name/version and let the linker figure out the path.
+    if(NOT PYTHON_LIBRARY)
+        set(PYTHON_LIBRARY python${PYTHON_LIBRARY_SUFFIX})
+    endif()
+endif()
+
+MARK_AS_ADVANCED(
+  PYTHON_LIBRARY
+  PYTHON_INCLUDE_DIR
+)
+
+# We use PYTHON_INCLUDE_DIR, PYTHON_LIBRARY and PYTHON_DEBUG_LIBRARY for the
+# cache entries because they are meant to specify the location of a single
+# library. We now set the variables listed by the documentation for this
+# module.
+SET(PYTHON_INCLUDE_DIRS "${PYTHON_INCLUDE_DIR}")
+SET(PYTHON_LIBRARIES "${PYTHON_LIBRARY}")
+SET(PYTHON_DEBUG_LIBRARIES "${PYTHON_DEBUG_LIBRARY}")
+
+find_package_message(PYTHON
+    "Found PythonLibs: ${PYTHON_LIBRARY}"
+    "${PYTHON_EXECUTABLE}${PYTHON_VERSION}")
+
+set(PYTHONLIBS_FOUND TRUE)

dlib/external/pybind11/tools/check-style.sh

+#!/bin/bash
+#
+# Script to check include/test code for common pybind11 code style errors.
+#
+# This script currently checks for
+#
+# 1. use of tabs instead of spaces
+# 2. MSDOS-style CRLF endings
+# 3. trailing spaces
+# 4. missing space between keyword and parenthesis, e.g.: for(, if(, while(
+# 5. Missing space between right parenthesis and brace, e.g. 'for (...){'
+# 6. opening brace on its own line. It should always be on the same line as the
+#    if/while/for/do statement.
+#
+# Invoke as: tools/check-style.sh
+#
+
+check_style_errors=0
+IFS=$'\n'
+
+found="$( GREP_COLORS='mt=41' GREP_COLOR='41' grep $'\t' include tests/*.{cpp,py,h} docs/*.rst -rn --color=always )"
+if [ -n "$found" ]; then
+    # The mt=41 sets a red background for matched tabs:
+    echo -e '\033[31;01mError: found tab characters in the following files:\033[0m'
+    check_style_errors=1
+    echo "$found" | sed -e 's/^/    /'
+fi
+
+
+found="$( grep -IUlr $'\r' include tests/*.{cpp,py,h} docs/*.rst --color=always )"
+if [ -n "$found" ]; then
+    echo -e '\033[31;01mError: found CRLF characters in the following files:\033[0m'
+    check_style_errors=1
+    echo "$found" | sed -e 's/^/    /'
+fi
+
+found="$(GREP_COLORS='mt=41' GREP_COLOR='41' grep '[[:blank:]]\+$' include tests/*.{cpp,py,h} docs/*.rst -rn --color=always )"
+if [ -n "$found" ]; then
+    # The mt=41 sets a red background for matched trailing spaces
+    echo -e '\033[31;01mError: found trailing spaces in the following files:\033[0m'
+    check_style_errors=1
+    echo "$found" | sed -e 's/^/    /'
+fi
+
+found="$(grep '\<\(if\|for\|while\|catch\)(\|){' include tests/*.{cpp,h} -rn --color=always)"
+if [ -n "$found" ]; then
+    echo -e '\033[31;01mError: found the following coding style problems:\033[0m'
+    check_style_errors=1
+    echo "$found" | sed -e 's/^/    /'
+fi
+
+found="$(awk '
+function prefix(filename, lineno) {
+    return "    \033[35m" filename "\033[36m:\033[32m" lineno "\033[36m:\033[0m"
+}
+function mark(pattern, string) { sub(pattern, "\033[01;31m&\033[0m", string); return string }
+last && /^\s*{/ {
+    print prefix(FILENAME, FNR-1) mark("\\)\\s*$", last)
+    print prefix(FILENAME, FNR)   mark("^\\s*{", $0)
+    last=""
+}
+{ last = /(if|for|while|catch|switch)\s*\(.*\)\s*$/ ? $0 : "" }
+' $(find include -type f) tests/*.{cpp,h} docs/*.rst)"
+if [ -n "$found" ]; then
+    check_style_errors=1
+    echo -e '\033[31;01mError: braces should occur on the same line as the if/while/.. statement. Found issues in the following files:\033[0m'
+    echo "$found"
+fi
+
+exit $check_style_errors

dlib/external/pybind11/tools/libsize.py

+from __future__ import print_function, division
+import os
+import sys
+
+# Internal build script for generating debugging test .so size.
+# Usage:
+#     python libsize.py file.so save.txt -- displays the size of file.so and, if save.txt exists, compares it to the
+#                                           size in it, then overwrites save.txt with the new size for future runs.
+
+if len(sys.argv) != 3:
+    sys.exit("Invalid arguments: usage: python libsize.py file.so save.txt")
+
+lib = sys.argv[1]
+save = sys.argv[2]
+
+if not os.path.exists(lib):
+    sys.exit("Error: requested file ({}) does not exist".format(lib))
+
+libsize = os.path.getsize(lib)
+
+print("------", os.path.basename(lib), "file size:", libsize, end='')
+
+if os.path.exists(save):
+    with open(save) as sf:
+        oldsize = int(sf.readline())
+
+    if oldsize > 0:
+        change = libsize - oldsize
+        if change == 0:
+            print(" (no change)")
+        else:
+            print(" (change of {:+} bytes = {:+.2%})".format(change, change / oldsize))
+else:
+    print()
+
+with open(save, 'w') as sf:
+    sf.write(str(libsize))
+

dlib/external/pybind11/tools/mkdoc.py

+#!/usr/bin/env python3
+#
+#  Syntax: mkdoc.py [-I<path> ..] [.. a list of header files ..]
+#
+#  Extract documentation from C++ header files to use it in Python bindings
+#
+
+import os
+import sys
+import platform
+import re
+import textwrap
+
+from clang import cindex
+from clang.cindex import CursorKind
+from collections import OrderedDict
+from threading import Thread, Semaphore
+from multiprocessing import cpu_count
+
+RECURSE_LIST = [
+    CursorKind.TRANSLATION_UNIT,
+    CursorKind.NAMESPACE,
+    CursorKind.CLASS_DECL,
+    CursorKind.STRUCT_DECL,
+    CursorKind.ENUM_DECL,
+    CursorKind.CLASS_TEMPLATE
+]
+
+PRINT_LIST = [
+    CursorKind.CLASS_DECL,
+    CursorKind.STRUCT_DECL,
+    CursorKind.ENUM_DECL,
+    CursorKind.ENUM_CONSTANT_DECL,
+    CursorKind.CLASS_TEMPLATE,
+    CursorKind.FUNCTION_DECL,
+    CursorKind.FUNCTION_TEMPLATE,
+    CursorKind.CONVERSION_FUNCTION,
+    CursorKind.CXX_METHOD,
+    CursorKind.CONSTRUCTOR,
+    CursorKind.FIELD_DECL
+]
+
+CPP_OPERATORS = {
+    '<=': 'le', '>=': 'ge', '==': 'eq', '!=': 'ne', '[]': 'array',
+    '+=': 'iadd', '-=': 'isub', '*=': 'imul', '/=': 'idiv', '%=':
+    'imod', '&=': 'iand', '|=': 'ior', '^=': 'ixor', '<<=': 'ilshift',
+    '>>=': 'irshift', '++': 'inc', '--': 'dec', '<<': 'lshift', '>>':
+    'rshift', '&&': 'land', '||': 'lor', '!': 'lnot', '~': 'bnot',
+    '&': 'band', '|': 'bor', '+': 'add', '-': 'sub', '*': 'mul', '/':
+    'div', '%': 'mod', '<': 'lt', '>': 'gt', '=': 'assign', '()': 'call'
+}
+
+CPP_OPERATORS = OrderedDict(
+    sorted(CPP_OPERATORS.items(), key=lambda t: -len(t[0])))
+
+job_count = cpu_count()
+job_semaphore = Semaphore(job_count)
+
+output = []
+
+def d(s):
+    return s.decode('utf8')
+
+
+def sanitize_name(name):
+    name = re.sub(r'type-parameter-0-([0-9]+)', r'T\1', name)
+    for k, v in CPP_OPERATORS.items():
+        name = name.replace('operator%s' % k, 'operator_%s' % v)
+    name = re.sub('<.*>', '', name)
+    name = ''.join([ch if ch.isalnum() else '_' for ch in name])
+    name = re.sub('_$', '', re.sub('_+', '_', name))
+    return '__doc_' + name
+
+
+def process_comment(comment):
+    result = ''
+
+    # Remove C++ comment syntax
+    leading_spaces = float('inf')
+    for s in comment.expandtabs(tabsize=4).splitlines():
+        s = s.strip()
+        if s.startswith('/*'):
+            s = s[2:].lstrip('*')
+        elif s.endswith('*/'):
+            s = s[:-2].rstrip('*')
+        elif s.startswith('///'):
+            s = s[3:]
+        if s.startswith('*'):
+            s = s[1:]
+        if len(s) > 0:
+            leading_spaces = min(leading_spaces, len(s) - len(s.lstrip()))
+        result += s + '\n'
+
+    if leading_spaces != float('inf'):
+        result2 = ""
+        for s in result.splitlines():
+            result2 += s[leading_spaces:] + '\n'
+        result = result2
+
+    # Doxygen tags
+    cpp_group = '([\w:]+)'
+    param_group = '([\[\w:\]]+)'
+
+    s = result
+    s = re.sub(r'\\c\s+%s' % cpp_group, r'``\1``', s)
+    s = re.sub(r'\\a\s+%s' % cpp_group, r'*\1*', s)
+    s = re.sub(r'\\e\s+%s' % cpp_group, r'*\1*', s)
+    s = re.sub(r'\\em\s+%s' % cpp_group, r'*\1*', s)
+    s = re.sub(r'\\b\s+%s' % cpp_group, r'**\1**', s)
+    s = re.sub(r'\\ingroup\s+%s' % cpp_group, r'', s)
+    s = re.sub(r'\\param%s?\s+%s' % (param_group, cpp_group),
+               r'\n\n$Parameter ``\2``:\n\n', s)
+    s = re.sub(r'\\tparam%s?\s+%s' % (param_group, cpp_group),
+               r'\n\n$Template parameter ``\2``:\n\n', s)
+
+    for in_, out_ in {
+        'return': 'Returns',
+        'author': 'Author',
+        'authors': 'Authors',
+        'copyright': 'Copyright',
+        'date': 'Date',
+        'remark': 'Remark',
+        'sa': 'See also',
+        'see': 'See also',
+        'extends': 'Extends',
+        'throw': 'Throws',
+        'throws': 'Throws'
+    }.items():
+        s = re.sub(r'\\%s\s*' % in_, r'\n\n$%s:\n\n' % out_, s)
+
+    s = re.sub(r'\\details\s*', r'\n\n', s)
+    s = re.sub(r'\\brief\s*', r'', s)
+    s = re.sub(r'\\short\s*', r'', s)
+    s = re.sub(r'\\ref\s*', r'', s)
+
+    s = re.sub(r'\\code\s?(.*?)\s?\\endcode',
+               r"```\n\1\n```\n", s, flags=re.DOTALL)
+
+    # HTML/TeX tags
+    s = re.sub(r'<tt>(.*?)</tt>', r'``\1``', s, flags=re.DOTALL)
+    s = re.sub(r'<pre>(.*?)</pre>', r"```\n\1\n```\n", s, flags=re.DOTALL)
+    s = re.sub(r'<em>(.*?)</em>', r'*\1*', s, flags=re.DOTALL)
+    s = re.sub(r'<b>(.*?)</b>', r'**\1**', s, flags=re.DOTALL)
+    s = re.sub(r'\\f\$(.*?)\\f\$', r'$\1$', s, flags=re.DOTALL)
+    s = re.sub(r'<li>', r'\n\n* ', s)
+    s = re.sub(r'</?ul>', r'', s)
+    s = re.sub(r'</li>', r'\n\n', s)
+
+    s = s.replace('``true``', '``True``')
+    s = s.replace('``false``', '``False``')
+
+    # Re-flow text
+    wrapper = textwrap.TextWrapper()
+    wrapper.expand_tabs = True
+    wrapper.replace_whitespace = True
+    wrapper.drop_whitespace = True
+    wrapper.width = 70
+    wrapper.initial_indent = wrapper.subsequent_indent = ''
+
+    result = ''
+    in_code_segment = False
+    for x in re.split(r'(```)', s):
+        if x == '```':
+            if not in_code_segment:
+                result += '```\n'
+            else:
+                result += '\n```\n\n'
+            in_code_segment = not in_code_segment
+        elif in_code_segment:
+            result += x.strip()
+        else:
+            for y in re.split(r'(?: *\n *){2,}', x):
+                wrapped = wrapper.fill(re.sub(r'\s+', ' ', y).strip())
+                if len(wrapped) > 0 and wrapped[0] == '$':
+                    result += wrapped[1:] + '\n'
+                    wrapper.initial_indent = \
+                        wrapper.subsequent_indent = ' ' * 4
+                else:
+                    if len(wrapped) > 0:
+                        result += wrapped + '\n\n'
+                    wrapper.initial_indent = wrapper.subsequent_indent = ''
+    return result.rstrip().lstrip('\n')
+
+
+def extract(filename, node, prefix):
+    if not (node.location.file is None or
+            os.path.samefile(d(node.location.file.name), filename)):
+        return 0
+    if node.kind in RECURSE_LIST:
+        sub_prefix = prefix
+        if node.kind != CursorKind.TRANSLATION_UNIT:
+            if len(sub_prefix) > 0:
+                sub_prefix += '_'
+            sub_prefix += d(node.spelling)
+        for i in node.get_children():
+            extract(filename, i, sub_prefix)
+    if node.kind in PRINT_LIST:
+        comment = d(node.raw_comment) if node.raw_comment is not None else ''
+        comment = process_comment(comment)
+        sub_prefix = prefix
+        if len(sub_prefix) > 0:
+            sub_prefix += '_'
+        if len(node.spelling) > 0:
+            name = sanitize_name(sub_prefix + d(node.spelling))
+            global output
+            output.append((name, filename, comment))
+
+
+class ExtractionThread(Thread):
+    def __init__(self, filename, parameters):
+        Thread.__init__(self)
+        self.filename = filename
+        self.parameters = parameters
+        job_semaphore.acquire()
+
+    def run(self):
+        print('Processing "%s" ..' % self.filename, file=sys.stderr)
+        try:
+            index = cindex.Index(
+                cindex.conf.lib.clang_createIndex(False, True))
+            tu = index.parse(self.filename, self.parameters)
+            extract(self.filename, tu.cursor, '')
+        finally:
+            job_semaphore.release()
+
+if __name__ == '__main__':
+    parameters = ['-x', 'c++', '-std=c++11']
+    filenames = []
+
+    if platform.system() == 'Darwin':
+        dev_path = '/Applications/Xcode.app/Contents/Developer/'
+        lib_dir = dev_path + 'Toolchains/XcodeDefault.xctoolchain/usr/lib/'
+        sdk_dir = dev_path + 'Platforms/MacOSX.platform/Developer/SDKs'
+        libclang = lib_dir + 'libclang.dylib'
+
+        if os.path.exists(libclang):
+            cindex.Config.set_library_path(os.path.dirname(libclang))
+
+        if os.path.exists(sdk_dir):
+            sysroot_dir = os.path.join(sdk_dir, next(os.walk(sdk_dir))[1][0])
+            parameters.append('-isysroot')
+            parameters.append(sysroot_dir)
+
+    for item in sys.argv[1:]:
+        if item.startswith('-'):
+            parameters.append(item)
+        else:
+            filenames.append(item)
+
+    if len(filenames) == 0:
+        print('Syntax: %s [.. a list of header files ..]' % sys.argv[0])
+        exit(-1)
+
+    print('''/*
+  This file contains docstrings for the Python bindings.
+  Do not edit! These were automatically extracted by mkdoc.py
+ */
+
+#define __EXPAND(x)                                      x
+#define __COUNT(_1, _2, _3, _4, _5, _6, _7, COUNT, ...)  COUNT
+#define __VA_SIZE(...)                                   __EXPAND(__COUNT(__VA_ARGS__, 7, 6, 5, 4, 3, 2, 1))
+#define __CAT1(a, b)                                     a ## b
+#define __CAT2(a, b)                                     __CAT1(a, b)
+#define __DOC1(n1)                                       __doc_##n1
+#define __DOC2(n1, n2)                                   __doc_##n1##_##n2
+#define __DOC3(n1, n2, n3)                               __doc_##n1##_##n2##_##n3
+#define __DOC4(n1, n2, n3, n4)                           __doc_##n1##_##n2##_##n3##_##n4
+#define __DOC5(n1, n2, n3, n4, n5)                       __doc_##n1##_##n2##_##n3##_##n4##_##n5
+#define __DOC6(n1, n2, n3, n4, n5, n6)                   __doc_##n1##_##n2##_##n3##_##n4##_##n5##_##n6
+#define __DOC7(n1, n2, n3, n4, n5, n6, n7)               __doc_##n1##_##n2##_##n3##_##n4##_##n5##_##n6##_##n7
+#define DOC(...)                                         __EXPAND(__EXPAND(__CAT2(__DOC, __VA_SIZE(__VA_ARGS__)))(__VA_ARGS__))
+
+#if defined(__GNUG__)
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wunused-variable"
+#endif
+''')
+
+    output.clear()
+    for filename in filenames:
+        thr = ExtractionThread(filename, parameters)
+        thr.start()
+
+    print('Waiting for jobs to finish ..', file=sys.stderr)
+    for i in range(job_count):
+        job_semaphore.acquire()
+
+    name_ctr = 1
+    name_prev = None
+    for name, _, comment in list(sorted(output, key=lambda x: (x[0], x[1]))):
+        if name == name_prev:
+            name_ctr += 1
+            name = name + "_%i" % name_ctr
+        else:
+            name_prev = name
+            name_ctr = 1
+        print('\nstatic const char *%s =%sR"doc(%s)doc";' %
+              (name, '\n' if '\n' in comment else ' ', comment))
+
+    print('''
+#if defined(__GNUG__)
+#pragma GCC diagnostic pop
+#endif
+''')

dlib/external/pybind11/tools/pybind11Config.cmake.in

+# pybind11Config.cmake
+# --------------------
+#
+# PYBIND11 cmake module.
+# This module sets the following variables in your project::
+#
+#   pybind11_FOUND - true if pybind11 and all required components found on the system
+#   pybind11_VERSION - pybind11 version in format Major.Minor.Release
+#   pybind11_INCLUDE_DIRS - Directories where pybind11 and python headers are located.
+#   pybind11_INCLUDE_DIR - Directory where pybind11 headers are located.
+#   pybind11_DEFINITIONS - Definitions necessary to use pybind11, namely USING_pybind11.
+#   pybind11_LIBRARIES - compile flags and python libraries (as needed) to link against.
+#   pybind11_LIBRARY - empty.
+#   CMAKE_MODULE_PATH - appends location of accompanying FindPythonLibsNew.cmake and
+#                       pybind11Tools.cmake modules.
+#
+#
+# Available components: None
+#
+#
+# Exported targets::
+#
+# If pybind11 is found, this module defines the following :prop_tgt:`IMPORTED`
+# interface library targets::
+#
+#   pybind11::module - for extension modules
+#   pybind11::embed - for embedding the Python interpreter
+#
+# Python headers, libraries (as needed by platform), and the C++ standard
+# are attached to the target. Set PythonLibsNew variables to influence
+# python detection and PYBIND11_CPP_STANDARD (-std=c++11 or -std=c++14) to
+# influence standard setting. ::
+#
+#   find_package(pybind11 CONFIG REQUIRED)
+#   message(STATUS "Found pybind11 v${pybind11_VERSION}: ${pybind11_INCLUDE_DIRS}")
+#
+#   # Create an extension module
+#   add_library(mylib MODULE main.cpp)
+#   target_link_libraries(mylib pybind11::module)
+#
+#   # Or embed the Python interpreter into an executable
+#   add_executable(myexe main.cpp)
+#   target_link_libraries(myexe pybind11::embed)
+#
+# Suggested usage::
+#
+# find_package with version info is not recommended except for release versions. ::
+#
+#   find_package(pybind11 CONFIG)
+#   find_package(pybind11 2.0 EXACT CONFIG REQUIRED)
+#
+#
+# The following variables can be set to guide the search for this package::
+#
+#   pybind11_DIR - CMake variable, set to directory containing this Config file
+#   CMAKE_PREFIX_PATH - CMake variable, set to root directory of this package
+#   PATH - environment variable, set to bin directory of this package
+#   CMAKE_DISABLE_FIND_PACKAGE_pybind11 - CMake variable, disables
+#     find_package(pybind11) when not REQUIRED, perhaps to force internal build
+
+@PACKAGE_INIT@
+
+set(PN pybind11)
+
+# location of pybind11/pybind11.h
+set(${PN}_INCLUDE_DIR "${PACKAGE_PREFIX_DIR}/@CMAKE_INSTALL_INCLUDEDIR@")
+
+set(${PN}_LIBRARY "")
+set(${PN}_DEFINITIONS USING_${PN})
+
+check_required_components(${PN})
+
+# make detectable the FindPythonLibsNew.cmake module
+list(APPEND CMAKE_MODULE_PATH ${CMAKE_CURRENT_LIST_DIR})
+
+include(pybind11Tools)
+
+if(NOT (CMAKE_VERSION VERSION_LESS 3.0))
+#-----------------------------------------------------------------------------
+# Don't include targets if this file is being picked up by another
+# project which has already built this as a subproject
+#-----------------------------------------------------------------------------
+if(NOT TARGET ${PN}::pybind11)
+    include("${CMAKE_CURRENT_LIST_DIR}/${PN}Targets.cmake")
+
+    find_package(PythonLibsNew ${PYBIND11_PYTHON_VERSION} MODULE REQUIRED)
+    set_property(TARGET ${PN}::pybind11 APPEND PROPERTY INTERFACE_INCLUDE_DIRECTORIES ${PYTHON_INCLUDE_DIRS})
+    set_property(TARGET ${PN}::embed APPEND PROPERTY INTERFACE_LINK_LIBRARIES ${PYTHON_LIBRARIES})
+    if(WIN32 OR CYGWIN)
+      set_property(TARGET ${PN}::module APPEND PROPERTY INTERFACE_LINK_LIBRARIES ${PYTHON_LIBRARIES})
+    endif()
+
+    set_property(TARGET ${PN}::pybind11 APPEND PROPERTY INTERFACE_COMPILE_OPTIONS "${PYBIND11_CPP_STANDARD}")
+
+    get_property(_iid TARGET ${PN}::pybind11 PROPERTY INTERFACE_INCLUDE_DIRECTORIES)
+    get_property(_ill TARGET ${PN}::module PROPERTY INTERFACE_LINK_LIBRARIES)
+    set(${PN}_INCLUDE_DIRS ${_iid})
+    set(${PN}_LIBRARIES ${_ico} ${_ill})
+endif()
+endif()

dlib/external/pybind11/tools/pybind11Tools.cmake

+# tools/pybind11Tools.cmake -- Build system for the pybind11 modules
+#
+# Copyright (c) 2015 Wenzel Jakob <wenzel@inf.ethz.ch>
+#
+# All rights reserved. Use of this source code is governed by a
+# BSD-style license that can be found in the LICENSE file.
+
+cmake_minimum_required(VERSION 2.8.12)
+
+# Add a CMake parameter for choosing a desired Python version
+if(NOT PYBIND11_PYTHON_VERSION)
+  set(PYBIND11_PYTHON_VERSION "" CACHE STRING "Python version to use for compiling modules")
+endif()
+
+set(Python_ADDITIONAL_VERSIONS 3.7 3.6 3.5 3.4)
+find_package(PythonLibsNew ${PYBIND11_PYTHON_VERSION} REQUIRED)
+
+include(CheckCXXCompilerFlag)
+include(CMakeParseArguments)
+
+if(NOT PYBIND11_CPP_STANDARD AND NOT CMAKE_CXX_STANDARD)
+  if(NOT MSVC)
+    check_cxx_compiler_flag("-std=c++14" HAS_CPP14_FLAG)
+
+    if (HAS_CPP14_FLAG)
+      set(PYBIND11_CPP_STANDARD -std=c++14)
+    else()
+      check_cxx_compiler_flag("-std=c++11" HAS_CPP11_FLAG)
+      if (HAS_CPP11_FLAG)
+        set(PYBIND11_CPP_STANDARD -std=c++11)
+      else()
+        message(FATAL_ERROR "Unsupported compiler -- pybind11 requires C++11 support!")
+      endif()
+    endif()
+  elseif(MSVC)
+    set(PYBIND11_CPP_STANDARD /std:c++14)
+  endif()
+
+  set(PYBIND11_CPP_STANDARD ${PYBIND11_CPP_STANDARD} CACHE STRING
+      "C++ standard flag, e.g. -std=c++11, -std=c++14, /std:c++14.  Defaults to C++14 mode." FORCE)
+endif()
+
+# Checks whether the given CXX/linker flags can compile and link a cxx file.  cxxflags and
+# linkerflags are lists of flags to use.  The result variable is a unique variable name for each set
+# of flags: the compilation result will be cached base on the result variable.  If the flags work,
+# sets them in cxxflags_out/linkerflags_out internal cache variables (in addition to ${result}).
+function(_pybind11_return_if_cxx_and_linker_flags_work result cxxflags linkerflags cxxflags_out linkerflags_out)
+  set(CMAKE_REQUIRED_LIBRARIES ${linkerflags})
+  check_cxx_compiler_flag("${cxxflags}" ${result})
+  if (${result})
+    set(${cxxflags_out} "${cxxflags}" CACHE INTERNAL "" FORCE)
+    set(${linkerflags_out} "${linkerflags}" CACHE INTERNAL "" FORCE)
+  endif()
+endfunction()
+
+# Internal: find the appropriate link time optimization flags for this compiler
+function(_pybind11_add_lto_flags target_name prefer_thin_lto)
+  if (NOT DEFINED PYBIND11_LTO_CXX_FLAGS)
+    set(PYBIND11_LTO_CXX_FLAGS "" CACHE INTERNAL "")
+    set(PYBIND11_LTO_LINKER_FLAGS "" CACHE INTERNAL "")
+
+    if(CMAKE_CXX_COMPILER_ID MATCHES "GNU|Clang")
+      set(cxx_append "")
+      set(linker_append "")
+      if (CMAKE_CXX_COMPILER_ID MATCHES "Clang" AND NOT APPLE)
+        # Clang Gold plugin does not support -Os; append -O3 to MinSizeRel builds to override it
+        set(linker_append ";$<$<CONFIG:MinSizeRel>:-O3>")
+      elseif(CMAKE_CXX_COMPILER_ID MATCHES "GNU")
+        set(cxx_append ";-fno-fat-lto-objects")
+      endif()
+
+      if (CMAKE_CXX_COMPILER_ID MATCHES "Clang" AND prefer_thin_lto)
+        _pybind11_return_if_cxx_and_linker_flags_work(HAS_FLTO_THIN
+          "-flto=thin${cxx_append}" "-flto=thin${linker_append}"
+          PYBIND11_LTO_CXX_FLAGS PYBIND11_LTO_LINKER_FLAGS)
+      endif()
+
+      if (NOT HAS_FLTO_THIN)
+        _pybind11_return_if_cxx_and_linker_flags_work(HAS_FLTO
+          "-flto${cxx_append}" "-flto${linker_append}"
+          PYBIND11_LTO_CXX_FLAGS PYBIND11_LTO_LINKER_FLAGS)
+      endif()
+    elseif (CMAKE_CXX_COMPILER_ID MATCHES "Intel")
+      # Intel equivalent to LTO is called IPO
+      _pybind11_return_if_cxx_and_linker_flags_work(HAS_INTEL_IPO
+      "-ipo" "-ipo" PYBIND11_LTO_CXX_FLAGS PYBIND11_LTO_LINKER_FLAGS)
+    elseif(MSVC)
+      # cmake only interprets libraries as linker flags when they start with a - (otherwise it
+      # converts /LTCG to \LTCG as if it was a Windows path).  Luckily MSVC supports passing flags
+      # with - instead of /, even if it is a bit non-standard:
+      _pybind11_return_if_cxx_and_linker_flags_work(HAS_MSVC_GL_LTCG
+        "/GL" "-LTCG" PYBIND11_LTO_CXX_FLAGS PYBIND11_LTO_LINKER_FLAGS)
+    endif()
+
+    if (PYBIND11_LTO_CXX_FLAGS)
+      message(STATUS "LTO enabled")
+    else()
+      message(STATUS "LTO disabled (not supported by the compiler and/or linker)")
+    endif()
+  endif()
+
+  # Enable LTO flags if found, except for Debug builds
+  if (PYBIND11_LTO_CXX_FLAGS)
+    target_compile_options(${target_name} PRIVATE "$<$<NOT:$<CONFIG:Debug>>:${PYBIND11_LTO_CXX_FLAGS}>")
+  endif()
+  if (PYBIND11_LTO_LINKER_FLAGS)
+    target_link_libraries(${target_name} PRIVATE "$<$<NOT:$<CONFIG:Debug>>:${PYBIND11_LTO_LINKER_FLAGS}>")
+  endif()
+endfunction()
+
+# Build a Python extension module:
+# pybind11_add_module(<name> [MODULE | SHARED] [EXCLUDE_FROM_ALL]
+#                     [NO_EXTRAS] [THIN_LTO] source1 [source2 ...])
+#
+function(pybind11_add_module target_name)
+  set(options MODULE SHARED EXCLUDE_FROM_ALL NO_EXTRAS THIN_LTO)
+  cmake_parse_arguments(ARG "${options}" "" "" ${ARGN})
+
+  if(ARG_MODULE AND ARG_SHARED)
+    message(FATAL_ERROR "Can't be both MODULE and SHARED")
+  elseif(ARG_SHARED)
+    set(lib_type SHARED)
+  else()
+    set(lib_type MODULE)
+  endif()
+
+  if(ARG_EXCLUDE_FROM_ALL)
+    set(exclude_from_all EXCLUDE_FROM_ALL)
+  endif()
+
+  add_library(${target_name} ${lib_type} ${exclude_from_all} ${ARG_UNPARSED_ARGUMENTS})
+
+  target_include_directories(${target_name}
+    PRIVATE ${PYBIND11_INCLUDE_DIR}  # from project CMakeLists.txt
+    PRIVATE ${pybind11_INCLUDE_DIR}  # from pybind11Config
+    PRIVATE ${PYTHON_INCLUDE_DIRS})
+
+  # The prefix and extension are provided by FindPythonLibsNew.cmake
+  set_target_properties(${target_name} PROPERTIES PREFIX "${PYTHON_MODULE_PREFIX}")
+  set_target_properties(${target_name} PROPERTIES SUFFIX "${PYTHON_MODULE_EXTENSION}")
+
+  # -fvisibility=hidden is required to allow multiple modules compiled against
+  # different pybind versions to work properly, and for some features (e.g.
+  # py::module_local).  We force it on everything inside the `pybind11`
+  # namespace; also turning it on for a pybind module compilation here avoids
+  # potential warnings or issues from having mixed hidden/non-hidden types.
+  set_target_properties(${target_name} PROPERTIES CXX_VISIBILITY_PRESET "hidden")
+
+  if(WIN32 OR CYGWIN)
+    # Link against the Python shared library on Windows
+    target_link_libraries(${target_name} PRIVATE ${PYTHON_LIBRARIES})
+  elseif(APPLE)
+    # It's quite common to have multiple copies of the same Python version
+    # installed on one's system. E.g.: one copy from the OS and another copy
+    # that's statically linked into an application like Blender or Maya.
+    # If we link our plugin library against the OS Python here and import it
+    # into Blender or Maya later on, this will cause segfaults when multiple
+    # conflicting Python instances are active at the same time (even when they
+    # are of the same version).
+
+    # Windows is not affected by this issue since it handles DLL imports
+    # differently. The solution for Linux and Mac OS is simple: we just don't
+    # link against the Python library. The resulting shared library will have
+    # missing symbols, but that's perfectly fine -- they will be resolved at
+    # import time.
+
+    target_link_libraries(${target_name} PRIVATE "-undefined dynamic_lookup")
+
+    if(ARG_SHARED)
+      # Suppress CMake >= 3.0 warning for shared libraries
+      set_target_properties(${target_name} PROPERTIES MACOSX_RPATH ON)
+    endif()
+  endif()
+
+  # Make sure C++11/14 are enabled
+  target_compile_options(${target_name} PUBLIC ${PYBIND11_CPP_STANDARD})
+
+  if(ARG_NO_EXTRAS)
+    return()
+  endif()
+
+  _pybind11_add_lto_flags(${target_name} ${ARG_THIN_LTO})
+
+  if (NOT MSVC AND NOT ${CMAKE_BUILD_TYPE} MATCHES Debug)
+    # Strip unnecessary sections of the binary on Linux/Mac OS
+    if(CMAKE_STRIP)
+      if(APPLE)
+        add_custom_command(TARGET ${target_name} POST_BUILD
+                           COMMAND ${CMAKE_STRIP} -x $<TARGET_FILE:${target_name}>)
+      else()
+        add_custom_command(TARGET ${target_name} POST_BUILD
+                           COMMAND ${CMAKE_STRIP} $<TARGET_FILE:${target_name}>)
+      endif()
+    endif()
+  endif()
+
+  if(MSVC)
+    # /MP enables multithreaded builds (relevant when there are many files), /bigobj is
+    # needed for bigger binding projects due to the limit to 64k addressable sections
+    target_compile_options(${target_name} PRIVATE /MP /bigobj)
+  endif()
+endfunction()

dlib/python.h

@@ -3,7 +3,7 @@
 #ifndef DLIB_PYTHoN_TOP_
 #define DLIB_PYTHoN_TOP_ 
 
-#include "python/boost_python_utils.h"
+#include "python/pybind_utils.h"
 #include "python/pyassert.h"
 #include "python/serialize_pickle.h"
 #include "python/numpy.h"

dlib/python/numpy.h

@@ -3,22 +3,23 @@
 #ifndef DLIB_PYTHON_NuMPY_Hh_
 #define DLIB_PYTHON_NuMPY_Hh_
 
-#include <boost/python.hpp>
+#include <pybind11/pybind11.h>
 #include <dlib/error.h>
 #include <dlib/algs.h>
 #include <dlib/string.h>
 #include <dlib/array.h>
 #include <dlib/pixel.h>
 
+namespace py = pybind11;
+
 // ----------------------------------------------------------------------------------------
 
 template <typename T>
 void validate_numpy_array_type (
-    const boost::python::object& obj
+    const py::object& obj
 )
 {
-    using namespace boost::python;
-    const char ch = boost::python::extract<char>(obj.attr("dtype").attr("char"));
+    const char ch = obj.attr("dtype").attr("char").cast<char>();
 
     if (dlib::is_same_type<T,double>::value && ch != 'd')
         throw dlib::error("Expected numpy.ndarray of float64");
@@ -34,7 +35,7 @@ void validate_numpy_array_type (
 
 template <int dims>
 void get_numpy_ndarray_shape (
-    const boost::python::object& obj,
+    const py::object& obj,
     long (&shape)[dims]
 )
 /*!
@@ -73,7 +74,7 @@ void get_numpy_ndarray_shape (
 
 template <typename T, int dims>
 void get_numpy_ndarray_parts (
-    boost::python::object& obj,
+    py::object& obj,
     T*& data,
     dlib::array<T>& contig_buf,
     long (&shape)[dims]
@@ -123,7 +124,7 @@ void get_numpy_ndarray_parts (
 
 template <typename T, int dims>
 void get_numpy_ndarray_parts (
-    const boost::python::object& obj,
+    const py::object& obj,
     const T*& data,
     dlib::array<T>& contig_buf,
     long (&shape)[dims]

dlib/python/numpy_image.h

@@ -16,7 +16,7 @@ class numpy_gray_image
 public:
 
     numpy_gray_image() : _data(0), _nr(0), _nc(0) {}
-    numpy_gray_image (boost::python::object& img) 
+    numpy_gray_image (py::object& img) 
     {
         long shape[2];
         get_numpy_ndarray_parts(img, _data, _contig_buf, shape);
@@ -49,7 +49,7 @@ namespace dlib
 
 // ----------------------------------------------------------------------------------------
 
-inline bool is_gray_python_image (boost::python::object& img)
+inline bool is_gray_python_image (py::object& img)
 {
     try
     {
@@ -70,7 +70,7 @@ class numpy_rgb_image
 public:
 
     numpy_rgb_image() : _data(0), _nr(0), _nc(0) {}
-    numpy_rgb_image (boost::python::object& img) 
+    numpy_rgb_image (py::object& img) 
     {
         long shape[3];
         get_numpy_ndarray_parts(img, _data, _contig_buf, shape);
@@ -107,7 +107,7 @@ namespace dlib
 // ----------------------------------------------------------------------------------------
 
 
-inline bool is_rgb_python_image (boost::python::object& img)
+inline bool is_rgb_python_image (py::object& img)
 {
     try
     {