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C++ concepts: ReversibleContainer

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

Requirements

`X`	Container type
`T`	Element type
`a`, `b`	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

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 << '\n';
    }
}

Output:

Standard library

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