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C++ named requirements: ReversibleContainer

A ReversibleContainer is a Container that has iterators that meet the requirements of either LegacyBidirectionalIterator or LegacyRandomAccessIterator. Such iterators allow a ReversibleContainer to be iterated over in reverse.

Requirements

X Container type
T Element type
a Objects of type X

Types

Expression Return type Conditions
X::reverse_iterator Iterator type whose value type is T reverse_iterator<iterator>
X::const_reverse_iterator Constant iterator type whose value type is T reverse_iterator<const_iterator>

Member functions

Expression Return type Conditions Complexity
a.rbegin() reverse_iterator; const_reverse_iterator for constant a reverse_iterator(end()) Constant
a.rend() reverse_iterator; const_reverse_iterator for constant a reverse_iterator(begin()) Constant
a.crbegin() const_reverse_iterator const_cast<X const&>(a).rbegin() Constant
a.crend() const_reverse_iterator const_cast<X const&>(a).rend() Constant

Standard library

Example

The following example iterates over a vector (which has random-access iterators) in reverse.

#include <iostream>
#include <vector>
 
int main()
{
    std::vector<int> v = {3, 1, 4, 1, 5, 9};
 
    for (std::vector<int>::const_reverse_iterator i{v.crbegin()}; i != v.crend(); ++i)
        std::cout << *i << ' ';
    std::cout << '\n';
}

Output:

9 5 1 4 1 3

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