numpy.h: added array::squeeze() method

include/pybind11/numpy.h

@@ -109,6 +109,7 @@ struct npy_api {
     bool (*PyArray_EquivTypes_) (PyObject *, PyObject *);
     int (*PyArray_GetArrayParamsFromObject_)(PyObject *, PyObject *, char, PyObject **, int *,
                                              Py_ssize_t *, PyObject **, PyObject *);
+    PyObject *(*PyArray_Squeeze_)(PyObject *);
 private:
     enum functions {
         API_PyArray_Type = 2,
@@ -121,6 +122,7 @@ private:
         API_PyArray_DescrConverter = 174,
         API_PyArray_EquivTypes = 182,
         API_PyArray_GetArrayParamsFromObject = 278,
+        API_PyArray_Squeeze = 136
     };
 
     static npy_api lookup() {
@@ -143,6 +145,7 @@ private:
         DECL_NPY_API(PyArray_DescrConverter);
         DECL_NPY_API(PyArray_EquivTypes);
         DECL_NPY_API(PyArray_GetArrayParamsFromObject);
+        DECL_NPY_API(PyArray_Squeeze);
 #undef DECL_NPY_API
         return api;
     }
@@ -380,6 +383,12 @@ public:
         return offset_at(index...) / itemsize();
     }
 
+    /// Return a new view with all of the dimensions of length 1 removed
+    array squeeze() {
+        auto& api = detail::npy_api::get();
+        return array(api.PyArray_Squeeze_(m_ptr), false);
+    }
+
 protected:
     template<typename, typename> friend struct detail::npy_format_descriptor;
 
@@ -601,7 +610,7 @@ struct npy_format_descriptor<T, enable_if_t<is_pod_struct<T>::value>> {
         // 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) {
+                  [](const field_descriptor &a, const field_descriptor &b) {
                       return a.offset < b.offset;
                   });
         size_t offset = 0;