std::ranges::iter_move

inline namespace /* unspecified */ {
    inline constexpr /* unspecified */ iter_move = /* unspecified */;
}

template< class T >
    requires /* see below */
constexpr decltype(auto) iter_move( T&& t ) noexcept(/* see below */);

Obtains an rvalue reference or a prvalue temporary from a given iterator.

A ranges::iter_move(t) is expression-equivalent to:

1. iter_move(t), if t has a class or enumeration type and the expression is well-formed when treated as an unevaluated operand, where the overload resolution of iter_move is performed only with the candidates found by argument-dependent lookup.
2. Otherwise, std::move(*t) if *t is well-formed and is an lvalue.
3. Otherwise, *t if *t is well-formed and is an rvalue.

In all other cases, a call to ranges::iter_move is ill-formed, which can result in substitution failure when ranges::iter_move(e) appears in the immediate context of a template instantiation.

If ranges::iter_move(e) is not equal to *e, the program is ill-formed, no diagnostic required.

Customization point objects

The name ranges::iter_move 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_move_fn.

All instances of __iter_move_fn are equal. The effects of invoking different instances of type __iter_move_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_move 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_move above, __iter_move_fn models
.

• std::invocable<__iter_move_fn, Args...>,
• std::invocable<const __iter_move_fn, Args...>,
• std::invocable<__iter_move_fn&, Args...>, and
• std::invocable<const __iter_move_fn&, Args...>.
  

Otherwise, no function call operator of __iter_move_fn participates in overload resolution.

Example

See also