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	Complexity
X::reverse_iterator	iterator type whose value type is T	reverse_iterator<iterator>	compile time
X::const_reverse_iterator	constant iterator type whose value type is T	reverse_iterator<const_iterator>	compile time

Methods

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

• std::array
• std::deque
• std::list
• std::vector
• std::map
• std::multimap
• std::set
• std::multiset

Example

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

#include <vector>
#include <iostream>
 
int main()
{
    std::vector<int> v = {3, 1, 4, 1, 5, 9};
 
    for(std::vector<int>::reverse_iterator i = v.rbegin(); i != v.rend(); ++i) {
        std::cout << *i << ' ';
    }
}

Result

9 5 1 4 1 3