Allocator Requirements

The general utilities library requirements include requirements for allocators. Allocators are objects that contain information about the container. This includes information concerning pointer types, the type of their difference, the size of objects in this allocation, also the memory allocation and deallocation information. All of the standard containers are parameterized in terms of allocators.

The allocator class includes the following members

Table 1. Allocator Members
Expression	Meaning
pointer	A pointer to a type
const_pointer	A pointer to a const type
reference	A reference of a type
const_reference	A reference to a const type
value_type	A type identical to the type
size_type	An unsigned integer that can represent the largest object in the allocator
difference_type	A signed integer that can represent the difference between any to pointers in the allocator
rebind	The template member is effectively a typedef of the type to which the allocator is bound
address(type)	Returns the address of type
address(const type)	Returns the address of the const type
allocate(size)	Returns the allocation of size
allocate(size, address)	Returns the allocation of size at the address
max_size	The largest value that can be passed to allocate
Ax == Ay	Returns a bool true if the storage of each allocator can be deallocated by the other
Ax != Ay	Returns a bool true if the storage of each allocator can not be deallocated by the other
T()	Constructs an instance of type
T x(y)	x is constructed with the values of y

Allocator template parameters must meet additional requirements

All instances of an allocator are interchangeable and compare equal to each other
Members must meet the requirements in The Typedef Members Requirements

Implementation-defined allocators are allowed.

Table 2. The Typedef Members Requirements
Member	Type
pointer	T*
const_pointer	T const*
size_type	size_t
difference_type	ptrdiff_t