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std::ranges::end(3) C++ Standard Libary std::ranges::end(3) 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 ob- ject) } 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_refer- ence_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 ex- pression 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 im- mediate 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 poten- tially-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 differ- ent 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 inter- changeably. 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 implemen- tations. 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) http://cppreference.com 2022.07.31 std::ranges::end(3)
NAME | Synopsis | Notes | Example | Output: | See also
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