std::ranges::crend

Returns a sentinelfor the constant iterator(since C++23) indicating the end of a const-qualified(until C++23)

If ranges::crend(e) is valid for an expression e, where decltype((e)) is T, then CT models std::ranges::range, and (until C++23) std::sentinel_for<S, I> is true in all cases, where S is decltype(ranges::crend(e)) , and I is decltype( ranges::crbegin (e) ) . Additionally, S models constant-iterator if it models input_iterator (since C++23)

Customization point objects

The name ranges::crend denotes a customization point object, which is a const function object of a literal semiregular class type. For exposition purposes, the cv-unqualified version of its type is denoted as __crend_fn

All instances of __crend_fn are equal. The effects of invoking different instances of type __crend_fn on the same arguments are equivalent, regardless of whether the expression denoting the instance is an lvalue or rvalue, and is const-qualified or not (however, a volatile-qualified instance is not required to be invocable). Thus, ranges::crend

Given a set of types Args..., if std::declval <Args> ( ) meet the requirements for arguments to ranges::crend above, __crend_fn models

• std::invocable<__crend_fn, Args...>
• std::invocable < const __crend_fn, Args...>
• std::invocable <__crend_fn&, Args...>
• std::invocable < const __crend_fn&, Args...> .
  

Otherwise, no function call operator of __crend_fn participates in overload resolution.

Example

#include <algorithm>
#include <iostream>
#include <iterator>
#include <vector>
 
int main()
{
    int a[]{4, 6, -3, 9, 10};
    std::cout << "Array backwards: ";
    namespace ranges = std::ranges;
    ranges::copy(ranges::rbegin(a), ranges::rend(a),
                 std::ostream_iterator<int>(std::cout, " "));
    std::cout << '\n';
 
    std::cout << "Vector backwards: ";
    std::vector v{4, 6, -3, 9, 10};
    ranges::copy(ranges::rbegin(v), ranges::rend(v),
                 std::ostream_iterator<int>(std::cout, " "));
    std::cout << '\n';
}

Array backwards: 10 9 -3 6 4
Vector backwards: 10 9 -3 6 4

See also