std::ranges::iter_swap
Defined in header <iterator>
|
||
namespace ranges { inline namespace /* unspecified */ { |
(since C++20) (customization 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> |
(exposition only*) | |
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:
- (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], excludingstd::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.
- Otherwise, ranges::swap(*i1, *i2) if both
I1
andI2
modelindirectly_readable
and if std::iter_reference_t<I1> and std::iter_reference_t<I2> modelswappable_with
. - 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. - 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.
- ↑ 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.
[edit] Example
This section is incomplete Reason: no example |
[edit] See also
(C++20) |
swaps the objects pointed to by two adjusted underlying iterators (function template) |
(C++20) |
swaps the objects pointed to by two underlying iterators (function template) |
swaps the elements pointed to by two iterators (function template) |