stdcrend

std::crend is a function in the C++ standard library that returns a const_reverse_iterator to the end of a reversed range. Introduced in C++11 and defined in the<iterator> header, it is the const counterpart to std::rend and is used together with std::crbegin to perform read-only reverse iteration over a container or array.

Purpose and behavior

std::crend provides the end sentinel for reverse iteration. When paired with std::crbegin, it defines a range that yields elements in reverse order without allowing modification through the iterator. The value returned by std::crend corresponds to one element before the beginning of the container in reverse iteration, so a loop using crbegin and crend visits all elements from last to first.

Typical usage

A common pattern is:

- for (auto it = std::crbegin(v); it != std::crend(v); ++it) { use *it; }

This will access the elements of v in reverse order without mutating them. For readability, some code favors range-based loops with explicit reverse iteration where appropriate.

Relation to other iterators

std::crend is the const version of std::rend and pairs with std::crbegin to enable read-only reverse traversal. It is distinct from std::rend, which yields a non-const reverse_iterator, allowing modification of elements through the reverse iterator.

Notes

There are overloads of std::crend for standard containers and for array types. In modern C++ (C++20 and later), ranges introduce additional concepts such as std::ranges::crend, providing similar functionality within the ranges framework.