Difference between revisions of "cpp/iterator/ranges/iter move"
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m (Removed 't', it only exists in the call signature.) |
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| − | {{cpp/ranges/title | iter_move}} | + | {{cpp/ranges/title|iter_move}} |
{{cpp/iterator/navbar}} | {{cpp/iterator/navbar}} | ||
{{dcl begin}} | {{dcl begin}} | ||
| − | {{dcl header | iterator}} | + | {{dcl header|iterator}} |
| − | {{dcl | notes={{mark custpt}} | since=c++20 | 1= | + | {{dcl|notes={{mark custpt}}|since=c++20|1= |
| − | inline namespace /*unspecified*/ { | + | inline namespace /* unspecified */ { |
| − | inline constexpr /*unspecified*/ iter_move = /*unspecified*/; | + | inline constexpr /* unspecified */ iter_move = /* unspecified */; |
} | } | ||
}} | }} | ||
{{dcl h|Call signature}} | {{dcl h|Call signature}} | ||
| − | {{dcl|1= | + | {{dcl|since=c++20|1= |
template< class T > | template< class T > | ||
requires /* see below */ | requires /* see below */ | ||
| − | constexpr decltype(auto) iter_move(T&& t) noexcept(/* see below */); | + | constexpr decltype(auto) iter_move( T&& t ) noexcept(/* see below */); |
}} | }} | ||
{{dcl end}} | {{dcl end}} | ||
| Line 19: | Line 19: | ||
Obtains an rvalue reference or a prvalue temporary from a given iterator. | Obtains an rvalue reference or a prvalue temporary from a given iterator. | ||
| − | + | A {{c|ranges::iter_move(t)}} is [[cpp/language/expressions#Expression-equivalence|expression-equivalent]] to: | |
| − | # {{c|iter_move | + | # {{c|iter_move(t)}}, if {{c|t}} has a class or enumeration type and the expression is well-formed when treated as an [[cpp/language/expressions#Potentially-evaluated expressions|unevaluated operand]], where the [[cpp/language/overload resolution|overload resolution]] of {{tt|iter_move}} is performed only with the candidates found by [[cpp/language/adl|argument-dependent lookup]]. |
| − | + | # Otherwise, {{c|std::move(*t)}} if {{c|*t}} is well-formed and is an lvalue. | |
| − | + | # Otherwise, {{c|*t}} if {{c|*t}} is well-formed and is an rvalue. | |
| − | # | + | |
| − | # | + | |
| − | In all other cases, a call to {{tt|ranges::iter_move}} is ill-formed, which can result in [[cpp/language/sfinae|substitution failure]] when {{c|ranges::iter_move( | + | In all other cases, a call to {{tt|ranges::iter_move}} is ill-formed, which can result in [[cpp/language/sfinae|substitution failure]] when {{c|ranges::iter_move(e)}} appears in the immediate context of a template instantiation. |
| − | If {{c|ranges::iter_move( | + | If {{c|ranges::iter_move(e)}} is not equal to {{c|*e}}, the program is ill-formed, no diagnostic required. |
| − | |||
{{cpp/ranges/cpo}} | {{cpp/ranges/cpo}} | ||
| + | |||
| + | ===Example=== | ||
| + | {{example}} | ||
===See also=== | ===See also=== | ||
{{dsc begin}} | {{dsc begin}} | ||
| − | {{dsc inc | cpp/iterator/adaptor/dsc iter_move | reverse_iterator}} | + | {{dsc inc|cpp/iterator/adaptor/dsc iter_move|reverse_iterator}} |
| − | {{dsc inc | cpp/iterator/adaptor/dsc iter_move | move_iterator}} | + | {{dsc inc|cpp/iterator/adaptor/dsc iter_move|move_iterator}} |
{{dsc end}} | {{dsc end}} | ||
{{langlinks|es|ja|zh}} | {{langlinks|es|ja|zh}} | ||
Latest revision as of 23:21, 5 May 2023
| Defined in header <iterator>
|
||
| inline namespace /* unspecified */ { inline constexpr /* unspecified */ iter_move = /* unspecified */; |
(since C++20) (customization point object) |
|
| Call signature |
||
| template< class T > requires /* see below */ |
(since C++20) | |
Obtains an rvalue reference or a prvalue temporary from a given iterator.
A ranges::iter_move(t) is expression-equivalent to:
- 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_moveis performed only with the candidates found by argument-dependent lookup. - Otherwise, std::move(*t) if *t is well-formed and is an lvalue.
- 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.
[edit] Example
| This section is incomplete Reason: no example |
[edit] See also
| (C++20) |
casts the result of dereferencing the adjusted underlying iterator to its associated rvalue reference type (function) |
| (C++20) |
casts the result of dereferencing the underlying iterator to its associated rvalue reference type (function) |
