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The size of the vector refers to the actual number of elements, while the capacity refers to the size of the internal array. When new elements are inserted, if the new size of the vector becomes larger than its capacity, reallocation occurs. [1] [5] This typically causes the vector to allocate a new region of storage, move the previously held ...
In C++ a std::vector object supports the store, select, and append operations with the performance characteristics discussed above. Vectors can be queried for their size and can be resized. Slower operations like inserting an element in the middle are also supported.
As a real-world example, the standard library fixed-size array type std::array is templated on both a type (representing the type of object that the array holds) and a number which is of type std::size_t (representing the number of elements the array holds). std::array can be declared as follows:
The maximum size of size_t is provided via SIZE_MAX, a macro constant which is defined in the <stdint.h> header (cstdint header in C++). size_t is guaranteed to be at least 16 bits wide. Additionally, POSIX includes ssize_t, which is a signed integer type of the same width as size_t.
The number of elements used by the dynamic array contents is its logical size or size, while the size of the underlying array is called the dynamic array's capacity or physical size, which is the maximum possible size without relocating data. [2] A fixed-size array will suffice in applications where the maximum logical size is fixed (e.g. by ...
These types were left out of the C++ standard; similar containers were standardized in C++11, but with different names (unordered_set and unordered_map). Other types of containers bitset stores series of bits similar to a fixed-sized vector of bools. Implements bitwise operations and lacks iterators. Not a sequence. Provides random access. valarray
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.
The variadic template feature of C++ was designed by Douglas Gregor and Jaakko Järvi [1] [2] and was later standardized in C++11. Prior to C++11, templates (classes and functions) could only take a fixed number of arguments, which had to be specified when a template was first declared.