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One common property of all sequential containers is that the elements can be accessed sequentially. Like all other standard library components, they reside in namespace std. The following containers are defined in the current revision of the C++ standard: array, vector, list, forward_list, deque.
The C++ Standard Library provides several generic containers, functions to use and manipulate these containers, function objects, generic strings and streams (including interactive and file I/O), support for some language features, and functions for common tasks such as finding the square root of a number.
Modern C++ compilers are tuned to minimize abstraction penalties arising from heavy use of the STL. The STL was created as the first library of generic algorithms and data structures for C++, with four ideas in mind: generic programming, abstractness without loss of efficiency, the Von Neumann computation model, [2] and value semantics.
For example, a container defined as std::vector<Shape*> does not work because Shape is not a class, but a template needing specialization. A container defined as std::vector<Shape<Circle>*> can only store Circles, not Squares. This is because each of the classes derived from the CRTP base class Shape is a unique type.
Like all C++ class templates, instantiations of standard library containers with different allocator arguments are distinct types. A function expecting an std::vector<int> argument will therefore only accept a vector instantiated with the default allocator.
It is, however, preferable to use an algorithm from the C++ Standard Library for such tasks. [1] [2] [3] The member function erase can be used to delete an element from a collection, but for containers which are based on an array, such as vector, all elements after the deleted element have to be moved forward to avoid "gaps" in the collection ...
In C++11, a move constructor of std::vector<T> that takes an rvalue reference to an std::vector<T> can copy the pointer to the internal C-style array out of the rvalue into the new std::vector<T>, then set the pointer inside the rvalue to null. Since the temporary will never again be used, no code will try to access the null pointer, and ...
The user defined function can be used as is in std::unordered_map, by passing it as a template parameter std :: unordered_map < X , int , hash_X > my_map ; Or can be set as the default hash function by specializing the std::hash function