std::ranges::end

Returns a sentinel indicating the end of a range.

If the argument is an lvalue or ranges::enable_borrowed_range < std::remove_cv_t <T>> is true, then a call to ranges::end is expression-equivalent

1. t + std::extent_v<T> if t has an array type of known bound.
   • If std::remove_all_extents_t < std::remove_reference_t <T>> is incomplete, then the call to ranges::end is ill-formed, no diagnostic required
2. Otherwise, decay-copy (t.end()) (until C++23) auto(t.end()) (since C++23) , if that expression is valid, and its type models std::sentinel_for < ranges::iterator_t <T>>
3. Otherwise, decay-copy (end(t)) (until C++23) auto(end(t)) (since C++23) , if T is a class or enumeration type, that expression is valid and its converted type models std::sentinel_for < ranges::iterator_t <T>> , where the meaning of end is established as if by performing argument-dependent lookup

In all other cases, a call to ranges::end is ill-formed, which can result in substitution failure when the call to ranges::end

Customization point objects

The name ranges::end 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 __end_fn

All instances of __end_fn are equal. The effects of invoking different instances of type __end_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::end

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

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

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

Notes

If the argument is an rvalue (i.e. T is an object type) and ranges::enable_borrowed_range < std::remove_cv_t <T>> is false, or if it is of an array type of unknown bound, the call to ranges::end

If ranges:: end ( std::forward <T> (t) ) is valid, then decltype(ranges:: end ( std::forward <T> (t) ) ) and decltype( ranges::begin ( std::forward <T> (t) ) ) model std::sentinel_for in all cases, while T models std::ranges::range

The C++20 standard requires that if the underlying end function call returns a prvalue, the return value is move-constructed from the materialized temporary object. All implementations directly return the prvalue instead. The requirement is corrected by the post-C++20 proposal P0849R8

Example

#include <algorithm>
#include <iostream>
#include <ranges>
#include <vector>
 
int main()
{
    std::vector<int> vec{3, 1, 4};
    if (std::ranges::find(vec, 5) != std::ranges::end(vec))
        std::cout << "found a 5 in vector vec!\n";
 
    int arr[]{5, 10, 15};
    if (std::ranges::find(arr, 5) != std::ranges::end(arr))
        std::cout << "found a 5 in array arr!\n";
}

found a 5 in array arr!

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

See also