# Containers

Many of these containers were inspired by the work of the Reusable Software Research Group at Ohio State. As such, many of the objects do not support copying in any form, only swapping is allowed. That is, when objects are added or removed from most of these containers they are swapped in and out, not copied.

This allows you to do things like have containers of containers of containers without encountering the overhead of the massive copying that would likely result if you did the same thing with the STL. It also means you can store objects that are not copyable inside these containers, which is not something you can do with the STL prior to C++11.

Note that it is assumed by these containers that swap() and operator< do not throw. They may not function correctly if this assumption is broken. Also note that the built in types (int, long, char, etc.) and std::string will not cause operator< or swap() to throw.

Note also that most of the containers inherit from the enumerable interface. Thus, all the member functions inherited from enumerable are defined in the enumerable class and their documentation is not repeated in each container's documentation. This includes the size() member function in each container.

Objects
static_set
any
any_trainer
any_function
any_decision_function
array
array2d
binary_search_tree
hash_map
hash_set
hash_table
directed_graph
graph
map
queue
reference_counter
type_safe_union
unordered_pair
sequence
set
stack
std_vector_c
static_map
sliding_buffer
circular_buffer
tuple
reference_wrapper
Interfaces
map_pair
enumerable
remover
remover dlib/interfaces/remover.h.html#remover asc_remover dlib/interfaces/remover.h.html#asc_remover pair_remover dlib/interfaces/remover.h.html#pair_remover asc_pair_remover dlib/interfaces/remover.h.html#asc_pair_remover
array
dlib/array.h
dlib/array/array_kernel_abstract.h
This object represents a 1-Dimensional array of objects.
sliding_buffer
dlib/sliding_buffer.h
dlib/sliding_buffer/sliding_buffer_kernel_abstract.h
This object represents an array with the ability to rotate its contents left or right. Note that the size of this object is always a power of two. If you need arbitrary sized objects then use a circular_buffer.
sliding_buffer_kernel_1
dlib/sliding_buffer/sliding_buffer_kernel_1.h
This object is implemented using a C style array in the obvious way. See the code for details.
kernel_1a
is a typedef for sliding_buffer_kernel_1
circular_buffer
dlib/sliding_buffer.h
dlib/sliding_buffer/circular_buffer_abstract.h
This object represents a simple sliding buffer which can contain and arbitrary number of elements.
array2d
dlib/array2d.h
dlib/array2d/array2d_kernel_abstract.h
This object represents a 2-Dimensional array of objects.
image_ex.cpp.html
binary_search_tree
dlib/binary_search_tree.h
dlib/binary_search_tree/binary_search_tree_kernel_abstract.h
This object represents a data dictionary that is built on top of some kind of binary search tree.
binary_search_tree_kernel_1
dlib/binary_search_tree/binary_search_tree_kernel_1.h
This implementation is done using an AVL binary search tree. It uses the memory_manager for all memory allocations.
kernel_1a
is a typedef for binary_search_tree_kernel_1
binary_search_tree_kernel_2
dlib/binary_search_tree/binary_search_tree_kernel_2.h
This implementation is done using a red-black binary search tree. It uses the memory_manager for all memory allocations.
kernel_2a
is a typedef for binary_search_tree_kernel_2
hash_map
dlib/hash_map.h
dlib/hash_map/hash_map_kernel_abstract.h
This object represents a hashed mapping of items of type domain onto items of type range.
hash_map_kernel_1
dlib/hash_map/hash_map_kernel_1.h
This implementation is done using a hash_table object. It uses the memory_manager for all memory allocations.

kernel_1a
is a typedef for hash_map_kernel_1 that uses hash_table_kernel_1a
kernel_1b
is a typedef for hash_map_kernel_1 that uses hash_table_kernel_2a
kernel_1c
is a typedef for hash_map_kernel_1 that uses hash_table_kernel_2b
hash_set
dlib/hash_set.h
dlib/hash_set/hash_set_kernel_abstract.h
This object represents a hashed unordered and unaddressed collection of unique items.
hash_set_kernel_1
dlib/hash_set/hash_set_kernel_1.h
This implementation is done using a hash_table object. It uses the memory_manager for all memory allocations.

kernel_1a
is a typedef for hash_set_kernel_1 that uses hash_table_kernel_1a
kernel_1b
is a typedef for hash_set_kernel_1 that uses hash_table_kernel_2a
kernel_1c
is a typedef for hash_set_kernel_1 that uses hash_table_kernel_2b
hash_table
dlib/hash_table.h
dlib/hash_table/hash_table_kernel_abstract.h
This object represents a data dictionary that is built on top of some kind of hash table.
hash_table_kernel_1
dlib/hash_table/hash_table_kernel_1.h
This implementation is done using singly linked lists as hashing buckets. It uses the memory_manager for all memory allocations.
kernel_1a
is a typedef for hash_table_kernel_1.
hash_table_kernel_2
dlib/hash_table/hash_table_kernel_2.h
This implementation is done using binary_search_tree objects as hashing buckets. It uses the memory_manager for all memory allocations.

kernel_2a
is a typedef for hash_table_kernel_2 that uses binary_search_tree_kernel_1
kernel_2b
is a typedef for hash_table_kernel_2 that uses binary_search_tree_kernel_2
map
dlib/map.h
dlib/map/map_kernel_abstract.h
This object represents a mapping of items of type domain onto items of type range.
map_kernel_1
dlib/map/map_kernel_1.h
This is implemented using the binary_search_tree component. It uses the memory_manager for all memory allocations.

kernel_1a
is a typedef for map_kernel_1 that uses binary_search_tree_kernel_1
kernel_1b
is a typedef for map_kernel_1 that uses binary_search_tree_kernel_2
enumerable
dlib/interfaces/enumerable.h
dlib/interfaces/enumerable.h
This object is an abstract class which represents an interface for iterating over all the elements of a container.
map_pair
dlib/interfaces/map_pair.h
dlib/interfaces/map_pair.h
This object is an abstract class which represents an interface for accessing a pair from a container such as the map, hash_table, etc.
remover
dlib/interfaces/remover.h
dlib/interfaces/remover.h
This is a set of interfaces which gives the ability to remove all the items in a container without actually knowing what kind of container contains them.
type_safe_union
dlib/type_safe_union.h
dlib/type_safe_union/type_safe_union_kernel_abstract.h
This object is a type safe analogue of the classic C union object. The type_safe_union, unlike a union, can contain non-POD types such as std::string.

It is also implemented without performing any heap memory allocations and instead it stores everything on the stack.

pipe_ex_2.cpp.html
bridge_ex.cpp.html
unordered_pair
dlib/unordered_pair.h
dlib/unordered_pair.h
This object is very similar to the std::pair struct except unordered_pair is only capable of representing an unordered set of two items rather than an ordered list of two items like std::pair.
any
dlib/any.h
dlib/any/any_abstract.h
This object is basically a type-safe version of a void*. In particular, it is a container which can contain only one object but the object may be of any type.

It is somewhat like the type_safe_union except you don't have to declare the set of possible content types beforehand. So in some sense this is like a less type-strict version of the type_safe_union.

any_decision_function
dlib/any.h
dlib/any/any_decision_function_abstract.h
This object is a version of dlib::any that is restricted to containing elements which are some kind of function object with an operator() with the following signature: result_type operator()(const sample_type&) const

It is intended to be used to contain dlib::decision_function objects and other types which represent learned decision functions. It allows you to write code which contains and processes these decision functions without needing to know the specific types of decision functions used.

any_function
dlib/any.h
dlib/any/any_function_abstract.h
This object is a version of dlib::any that is restricted to containing elements which are some kind of function or function object.
any_trainer
dlib/any.h
dlib/any/any_trainer_abstract.h
This object is a version of dlib::any that is restricted to containing elements which are some kind of object with a .train() method compatible with the following signature:

     decision_function train(
          const std::vector<sample_type>& samples,
          const std::vector<scalar_type>& labels
       ) const

Where decision_function is a type capable of being stored in an any_decision_function object.

any_trainer is intended to be used to contain objects such as the svm_nu_trainer and other similar types which represent supervised machine learning algorithms. It allows you to write code which contains and processes these trainer objects without needing to know the specific types of trainer objects used.

tuple
dlib/tuple.h
dlib/tuple/tuple_abstract.h
This is an implementation of a very simple templated container object. It contains between 0 and 31 objects where each object is listed explicitly in the tuple's template arguments.

Note that there is only one implementation of this object so there aren't any different kernels to choose from when you create instances of the tuple object. So for example, you could declare a tuple of 3 ints using the following statement: dlib::tuple<int,int,int> t;

reference_wrapper
dlib/ref.h
dlib/ref.h
This is a simple object that just holds a reference to another object. It is useful because it can serve as a kind of "copyable reference".
thread_function_ex.cpp.html
graph
dlib/graph.h
dlib/graph/graph_kernel_abstract.h
This object represents a graph which is a set of nodes with undirected edges connecting various nodes.
graph_kernel_1
dlib/graph/graph_kernel_1.h
This is implemented using std::vector to contain all the nodes and edges.
kernel_1a
is a typedef for graph_kernel_1
directed_graph
dlib/directed_graph.h
dlib/directed_graph/directed_graph_kernel_abstract.h
This object represents a directed graph which is a set of nodes with directed edges connecting various nodes.
directed_graph_kernel_1
dlib/directed_graph/directed_graph_kernel_1.h
This is implemented using std::vector to contain all the nodes and edges.
kernel_1a
is a typedef for directed_graph_kernel_1
queue
dlib/queue.h
dlib/queue/queue_kernel_abstract.h
This object represents a first in first out queue.
queue_ex.cpp.html
queue_kernel_1
dlib/queue/queue_kernel_1.h
This is implemented in the obvious way using a singly linked list. It does not use the memory_manager at all.
kernel_1a
is a typedef for queue_kernel_1
queue_kernel_2
dlib/queue/queue_kernel_2.h
This is implemented using a singly linked list and each node in the list contains block_size (a template parameter) elements. It uses the memory_manager for all memory allocations.
kernel_2a
is a typedef for queue_kernel_2 with a block_size of 20
kernel_2b
is a typedef for queue_kernel_2 with a block_size of 100
queue_sort
dlib/queue/queue_sort_abstract.h
This extension gives a queue the ability to sort its contents.
queue_sort_1
dlib/queue/queue_sort_1.h
This is a version of the QuickSort algorithm.
sort_1a
is a typedef for queue_kernel_1a extended by queue_sort_1
sort_1b
is a typedef for queue_kernel_2a extended by queue_sort_1
sort_1c
is a typedef for queue_kernel_2b extended by queue_sort_1
reference_counter
dlib/reference_counter.h
dlib/reference_counter/reference_counter_kernel_abstract.h
This object represents a container for an object and provides reference counting capabilities for the object it contains.
reference_counter_kernel_1
dlib/reference_counter/reference_counter_kernel_1.h
This implementation is done using pointers in the obvious way.
kernel_1a
is a typedef for reference_counter_kernel_1
sequence
dlib/sequence.h
dlib/sequence/sequence_kernel_abstract.h
This object represents an ordered sequence of items, each item is associated with an integer value. The items are numbered from 0 to the number of items in the sequence minus 1.
sequence_kernel_1
dlib/sequence/sequence_kernel_1.h
This is implemented as an AVL binary search tree. Accessing(or adding or removing) an element always takes O(log n) time. It uses the memory_manager for all memory allocations.
kernel_1a
is a typedef for sequence_kernel_1
sequence_kernel_2
dlib/sequence/sequence_kernel_2.h
This implementation is done using a doubly linked list in the shape of a ring. It will remember the last element accessed(or added or removed) and give O(1) access time to the elements just left and right of it. Aside from that, accessing(or adding or removing) a random element will take O(n) and in the worst case it will take time proportional to the size of the sequence/2.

It does not use the memory_manager at all.

kernel_2a
is a typedef for sequence_kernel_2
sequence_sort
dlib/sequence/sequence_sort_abstract.h
This extension gives a sequence the ability to sort its contents.
sequence_sort_1
dlib/sequence/sequence_sort_1.h
This is a version of the QuickSort algorithm and it sorts sequences of less than 30 elements with a selection sort. This implementation is fastest when used with sequence_kernel_2 and fairly slow when used with sequence_kernel_1
sort_1a
is a typedef for sequence_kernel_2a extended by sequence_sort_1
sequence_sort_2
dlib/sequence/sequence_sort_2.h
This is a version of the QuickSort algorithm. This implementation of sort is the best to use with sequence_kernel_1 objects but gives extremely poor performance with sequence_kernel_2 objects.
sort_2a
is a typedef for sequence_kernel_1a extended by sequence_sort_2
sequence_compare
dlib/sequence/sequence_compare_abstract.h
This extension gives sequences the ability to compare themselves using operator< and operator==. Thus they can be used in the other container classes that require this ability. (maps, sets, etc.)
sequence_compare_1
dlib/sequence/sequence_compare_1.h
The implementation is obvious. Click on the sequence_compare_1 link if you want to see.
compare_1a
is a typedef for sequence_kernel_1a extended by sequence_compare_1
compare_1b
is a typedef for sequence_kernel_2a extended by sequence_compare_1
set
dlib/set.h
dlib/set/set_kernel_abstract.h
This object represents an unordered and unaddressed collection of unique items.
set_kernel_1
dlib/set/set_kernel_1.h
This is implemented using the binary_search_tree component. It uses the memory_manager for all memory allocations.

kernel_1a
is a typedef for set_kernel_1 that uses binary_search_tree_kernel_1
kernel_1b
is a typedef for set_kernel_1 that uses binary_search_tree_kernel_2
set_compare
dlib/set/set_compare_abstract.h
This extension gives sets the ability to compare themselves using operator< and operator==. Thus they can be used in the other container classes that require this ability. (maps, sets, etc.)
set_compare_1
dlib/set/set_compare_1.h
The implementation is obvious. Click on the set_compare_1 link if you want to see.
compare_1a
is a typedef for set_kernel_1a extended by set_compare_1
compare_1b
is a typedef for set_kernel_1b extended by set_compare_1
stack
dlib/stack.h
dlib/stack/stack_kernel_abstract.h
This object represents a last in first out stack.
stack_kernel_1
dlib/stack/stack_kernel_1.h
This implementation is done in the obvious way using a singly linked list. It uses the memory_manager for all memory allocations.

kernel_1a
is a typedef for stack_kernel_1
static_map
dlib/static_map.h
dlib/static_map/static_map_kernel_abstract.h
This object represents a mapping of items of type domain onto items of type range. The difference between this object and the normal map object is that it does not support adding or removing individual objects from itself. This allows implementations to focus on using less memory and achieving faster searching.
static_map_kernel_1
dlib/static_map/static_map_kernel_1.h
This implementation is just a sorted array which can be searched using a binary search.
kernel_1a
is a typedef for static_map_kernel_1
static_set
dlib/static_set.h
dlib/static_set/static_set_kernel_abstract.h
This object represents an unordered and unaddressed collection of items. The difference between this object and the normal set object is that it does not support adding or removing individual objects from itself. This allows implementations to focus on using less memory and achieving faster searching.
static_set_kernel_1
dlib/static_set/static_set_kernel_1.h
This implementation is just a sorted array which can be searched using a binary search.
kernel_1a
is a typedef for static_set_kernel_1
static_set_compare
dlib/static_set/static_set_compare_abstract.h
This extension gives static_sets the ability to compare themselves using operator< and operator==. Thus they can be used in the other container classes that require this ability. (maps, static_sets, etc.)
static_set_compare_1
dlib/static_set/static_set_compare_1.h
The implementation is obvious. Click on the static_set_compare_1 link if you want to see.
compare_1a
is a typedef for static_set_kernel_1a extended by static_set_compare_1
std_vector_c
dlib/stl_checked.h
dlib/stl_checked/std_vector_c_abstract.h
This object is a simple wrapper around the std::vector object. It provides an identical interface but also checks the preconditions of each member function. That is, if you violate a requires clause the dlib::fatal_error exception is thrown.