C++ named requirements: Container

A Container is an object used to store other objects and taking care of the management of the memory used by the objects it contains.

Requirements

C container type;
T element type;
a, b objects of type C.

Types

name	type	notes
`value_type`	T	Eraseable
`reference`	T&
`const_reference`	const T&
`iterator`	iterator pointing to T	LegacyForwardIterator convertible to `const_iterator`
`const_iterator`	const iterator pointing to T	LegacyForwardIterator
`difference_type`	signed integer	must be the same as `iterator_traits::difference_type` for `iterator` and `const_iterator`
`size_type`	unsigned integer	large enough to represent all positive values of `difference_type`

Methods and operators

expression	return type	semantics	conditions	complexity
C()	C	creates an empty container	Post: C().empty() == true	Constant
C(a)	C	creates a copy of `a`	Pre: T must be CopyInsertable Post: a == C(a)	Linear
a = b	C&	destroys or move-assigns all elements of `a` from elements of `b`	Post: a == b	Linear
a.~C()	void	destroys all elements of `a` and frees all memory		Linear
a.begin()	(const_)iterator	Iterator to the first element of `a`		Constant
a.end()	(const_)iterator	Iterator to one past the last element of `a`		Constant
a.cbegin()(since C++11)	const_iterator	const_cast<const C&>(a).begin()		Constant
a.cend()(since C++11)	const_iterator	const_cast<const C&>(a).end()		Constant
a == b	convertible to bool	std::equal(a.begin(), a.end(), b.begin(), b.end())(since C++14)	Pre: T must be EqualityComparable	Constant^[1] if `a.size() != b.size()`, linear otherwise
a != b	convertible to bool	!(a == b)		Linear
a.swap(b)	void	exchanges the values of `a` and `b`		Constant^[2]^[3]
swap(a, b)	void	a.swap(b)		Constant^[2]
a.size()	size_type	distance(a.begin(), a.end())		Constant^[3]
a.max_size()	size_type	b.size() where `b` is the largest possible container		Constant^[3]
a.empty()	convertible to bool	a.begin() == a.end()		Constant
notes
↑ always linear for std::forward_list ↑ ^2.0 ^2.1 (since C++11) Linear for std::array ↑ ^3.0 ^3.1 ^3.2 (until C++11) Not strictly constant

Given

i and j, objects of a container's iterator type,

in the expressions i == j, i != j, i < j, i <= j, i >= j, i > j, i - j, either or both may be replaced by an object of the container's const_iterator type referring to the same element with no change in semantics.

(since C++14)

Container data races

see container thread safety

Other requirements

C

T

[1] ways linear for std::forward_list

[array-2] 2.0 ^2.1 (since C++11) Linear for std::array

[should-3] 3.0 ^3.1 ^3.2 (until C++11) Not strictly constant

[1]

[2]

[3]

Language
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Language support library
Concepts library (C++20)
Diagnostics library
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