std::ranges::iter_swap(3) C++ Standard Libary std::ranges::iter_swap(3) NAME std::ranges::iter_swap - std::ranges::iter_swap Synopsis Defined in header <iterator> namespace ranges { inline namespace /* unspecified */ { (since C++20) inline constexpr /* unspecified */ (customization iter_swap = /* unspecified */; point object) } } Call signature template< class I1, class I2 > constexpr void iter_swap( I1&& i1, I2&& i2 ) noexcept(/* see below (since C++20) */); Helper function template< class X, class Y > constexpr std::iter_value_t<X> iter-exchange-move( X&& x, Y&& y ) (exposition only*) noexcept(noexcept(std::iter_value_t<X>(std::ranges::iter_move(x))) && noexcept(*x = std::ranges::iter_move(y))); Swaps values denoted by two iterators. The effect of the exposition-only helper function iter-exchange-move is equivalent to std::iter_value_t<X> old(std::ranges::iter_move(x)); *x = std::ranges::iter_move(y); return old; ranges::iter_swap(i1, i2) is expression-equivalent to: 1. (void)iter_swap(i1, i2), if i1 or i2 has a class or enumeration type and the expression is well-formed, where the overload resolution of iter_swap is performed with the additional candidate void iter_swap(auto, auto) = delete;^[1], excluding std::ranges::iter_swap itself. * If the selected overload does not exchange the value denoted by i1 and i2, the program is ill-formed, no diagnostic required. 2. Otherwise, ranges::swap(*i1, *i2) if both I1 and I2 model indi- rectly_readable and if std::iter_reference_t<I1> and std::iter_reference_t<I2> model swappable_with. 3. Otherwise, (void)(*i1 = iter-exchange-move(i2, i1)), if std::indirectly_movable_storable<I1, I2> and std::indirectly_movable_storable<I2, I1> are both modeled, except that i1 is only evaluated once. 4. Otherwise, ranges::iter_swap(i1, i2) is ill-formed, which can result in substitution failure when ranges::iter_swap(i1, i2) appears in the immediate context of a template instantiation. 1. a This precludes calling unconstrained std::iter_swap. Customization point objects The name ranges::iter_swap denotes a customization point object, which is a const function object of a literal semiregular class type. For exposition pur- poses, the cv-unqualified version of its type is denoted as __iter_swap_fn. All instances of __iter_swap_fn are equal. The effects of invoking dif- ferent instances of type __iter_swap_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::iter_swap can be copied freely and its copies can be used interchangeably. Given a set of types Args..., if std::declval<Args>()... meet the re- quirements for arguments to ranges::iter_swap above, __iter_swap_fn models * std::invocable<__iter_swap_fn, Args...>, * std::invocable<const __iter_swap_fn, Args...>, * std::invocable<__iter_swap_fn&, Args...>, and * std::invocable<const __iter_swap_fn&, Args...>. Otherwise, no function call operator of __iter_swap_fn participates in overload resolution. Example This section is incomplete Reason: no example See also iter_swap swaps the objects pointed to by two adjusted underlying itera- tors (C++20) (function template) iter_swap swaps the objects pointed to by two underlying iterators (C++20) (function template) iter_swap swaps the elements pointed to by two iterators (function template) Category: * Todo no example http://cppreference.com 2024.06.10 std::ranges::iter_swap(3)
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