C++ concepts: Container

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Revision as of 15:26, 2 November 2012 by P12bot (Talk | contribs)


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.



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


name type notes
value_type T Destructible
reference lvalue of T
const_reference const lvalue of 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

Methods and operators

expression return type semantics conditions complexity
C(); C Creates an empty container Post: u.empty() == true Constant
C(a) C Create a copy of a Pre: T must be CopyInsertable
Post: a == X(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 Makes C EqualityComparable Pre: T must be EqualityComparable Linear
a != b convertible to bool !(a==b) Linear
a.swap(b) void exchanges the values of a and b Constant[1][2]
swap(a,b) void a.swap(b) Constant[1]
a.size() size_type distance(a.begin(),a.end()) Constant[2]
a.max_size() size_type b.size() where b is the largest possible container Constant[2]
a.empty() convertible to bool a.begin() == a.end() Constant
  1. 1.0 1.1 (since C++11) Linear for std::array
  2. 2.0 2.1 2.2 (until C++11) Not strictly constant

Container data races

Implementations are not required to provide any reentrancy guarantee for sequence modifications - it is not safe to push_back and read begin concurrently. However, it is required to avoid data races when the contents of the contained object in different elements of the same sequence are modified concurrently (except for vector<bool>). In other words, for a vector<int> with size greater than 1, x[1] = 5 and *x.begin() = 10 will not result in a data race.

These functions must also be considered const: begin, end, rbegin, rend, front, back, data, find, lower_bound, upper_bound, equal_range, at, and, except in AssociativeContainer and UnorderedAssociativeContainer, operator[]. Calling any of these functions concurrently will not result in a data race.

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