# std::ranges::end

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< cpp‎ | ranges

Defined in header `<ranges>` |  |
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 overload resolution is performed with the following candidates:
   - any declarations of `end` found by argument-dependent lookup.
   - void end(auto&) = delete;
   - void end(const auto&) = delete;

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. 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` can be copied freely and its copies can be used interchangeably.

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...>, and
- 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` 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.

### Example

Run this code

    #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";
    }

Output:

    found a 5 in array arr!

### See also

ranges::cend (C++20) | returns a sentinel indicating the end of a read-only range (customization point object)
ranges::begin (C++20) | returns an iterator to the beginning of a range (customization point object)
end cend (C++11)(C++14) | returns an iterator to the end of a container or array (function template)

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