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*/ {
inline constexpr /*unspecified*/ iter_swap = (since C++20)
/*unspecified*/; (customization point object)
}
}
Call signature
template< class I1, class I2 >
constexpr void iter_swap( I1&& i1, I2&& i2 ) (since
C++20)
noexcept(/* see below */);
Swaps values denoted by two iterators.
ranges::iter_swap(i1, i2 is expression-equivalent to:
1. (void)iter_swap(i1, i2), if std::remove_cvref_t<I1> or
std::remove_cvref_t<I2>
is a class or enumeration type and the expression is well-formed, where the
overload resolution is performed within namespace std::ranges with the
additional candidate:
* void iter_swap(auto, auto) = delete;
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>, where iter_exchange_move is
an
exposition-only function template described below (and 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(e1, e2) appears in the immediate
context of a template instantiation.
The exposition-only function template iter_exchange_move is defined the
equivalent
of:
template<class X, class Y>
constexpr std::iter_value_t<X> /*iter_exchange_move*/(X&& x,
Y&& y)
noexcept(noexcept(std::iter_value_t<X>(std::ranges::iter_move(x))
&&
noexcept(*x = std::ranges::iter_move(y))))
{
std::iter_value_t<X> old(std::ranges::iter_move(x));
*x = std::ranges::iter_move(y);
return old;
}
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::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.
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)
2022.07.31 | http://cppreference.com |