std::ranges::end - cppreference.com (original) (raw)

| Defined in header | | | | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | ------------------------------------------ | | Defined in header | | | | inline namespace /* unspecified */ { inline constexpr /* unspecified */ end = /* unspecified */; } | | (since C++20) (customization point object) | | Call signature | | | | template< class T > requires /* see below */ constexpr std::sentinel_for<ranges::iterator_t<T>> auto end( T&& t ); | | (since C++20) |

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 to:

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 only.

In all other cases, a call to ranges::end is ill-formed, which can result in substitution failure when the call to ranges::end appears in the immediate context of a template instantiation.

Customization point objects

The name ranges::end denotes a customization point object, which is a const function object of a literal semiregular class type. See CustomizationPointObject for details.

[edit] 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 is ill-formed, which also results in substitution failure.

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 to match the implementations.

[edit] Example

#include #include #include #include   int main() { std::vector 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"; }

Output:

[edit] Defect reports

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

[edit] See also

| | returns a sentinel indicating the end of a read-only range(customization point object)[edit] | | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | | returns an iterator to the beginning of a range(customization point object)[edit] | | | returns an iterator to the end of a container or array (function template) [edit] |