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 indirectly_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. ↑ 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 purposes, 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 different
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 requirements 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 iterators
(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