NAME¶

std::ranges::end - std::ranges::end

Synopsis¶

Defined in header <ranges>
inline namespace /*unspecified*/ {
(since C++20)
inline constexpr /*unspecified*/ end = /*unspecified*/; (customization point
object)
}
Call signature
template< class T >

requires /* see below */ (since C++20)

constexpr std::sentinel_for<ranges::iterator_t<T>> auto end(
T&& t );

Returns a sentinel indicating the end of a range.

range-begin-end.svg

Let t be an object of type T. 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, t.end() converted to its decayed type, if that expression with
conversion is valid, and its converted type models
std::sentinel_for<ranges::iterator_t<T>>.
3. Otherwise, end(t) converted to its decayed type, if t has a class or enumeration
type, the aforementioned unqualified call with conversion 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.

Expression-equivalent

Expression e is expression-equivalent to expression f, if

* e and f have the same effects, and
* either both are constant subexpressions or else neither is a constant
subexpression, and
* either both are potentially-throwing or else neither is potentially-throwing
(i.e. noexcept(e) == noexcept(f)).

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> v = { 3, 1, 4 };
namespace ranges = std::ranges;
if (ranges::find(v, 5) != ranges::end(v)) {
std::cout << "found a 5 in vector v!\n";
}

int a[] = { 5, 10, 15 };
if (ranges::find(a, 5) != ranges::end(a)) {
std::cout << "found a 5 in array a!\n";
}
}

Output:¶

found a 5 in array a!

See also¶

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