C++ concepts: Container

From cppreference.com
< cpp‎ | concept

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.


[edit] Requirements

  • C Container type
  • T Element type
  • a, b Objects of type C

[edit] Types

name type notes
value_type T Eraseable
reference T&
const_reference const T&
iterator iterator pointing to T ForwardIterator
convertible to const_iterator
const_iterator const iterator pointing to T ForwardIterator
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

[edit] Methods and operators

expression return type semantics conditions complexity
C() C Creates an empty container Post: C().empty() == true Constant
C(a) C Create a copy of a Pre: T must be CopyInsertable
Post: a == C(a)
a = b C& All elements of a are destroyed or move assigned to elements of b Post: a == b Linear
(&a)->~C() void Destroy all elements and free all memory Linear
a.begin() (const_)iterator Iterator to the first element Constant
a.end() (const_)iterator Iterator to one passed the last element 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
  1. always linear for std::forward_list
  2. 2.0 2.1 (since C++11) Linear for std::array
  3. 3.0 3.1 3.2 (until C++11) Not strictly constant


  • 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)

[edit] Container data races

see container thread safety

[edit] Other concepts