Difference between revisions of "cpp/iterator/indirect unary predicate"
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(Applied P2997R1 (Removing the common reference requirement from the indirectly invocable concepts).) |
(~ apply P2997R1 as DR20) |
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{{dcl begin}} | {{dcl begin}} | ||
{{dcl header|iterator}} | {{dcl header|iterator}} | ||
| − | + | {{dcl|since=c++20|1= | |
| − | {{dcl|since=c++20 | + | |
template< class F, class I > | template< class F, class I > | ||
concept indirect_unary_predicate = | concept indirect_unary_predicate = | ||
std::indirectly_readable<I> && | std::indirectly_readable<I> && | ||
std::copy_constructible<F> && | std::copy_constructible<F> && | ||
| − | std::predicate<F&, | + | std::predicate<F&, /*indirect-value-t*/<I>> && |
| − | + | ||
| − | + | ||
| − | + | ||
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std::predicate<F&, std::iter_reference_t<I>>; | std::predicate<F&, std::iter_reference_t<I>>; | ||
}} | }} | ||
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{{dcl end}} | {{dcl end}} | ||
The concept {{tt|indirect_unary_predicate}} specifies requirements for algorithms that call unary predicates as their arguments. The key difference between this concept and {{lc|std::predicate}} is that it is applied to the type that {{tt|I}} references, rather than {{tt|I}} itself. | The concept {{tt|indirect_unary_predicate}} specifies requirements for algorithms that call unary predicates as their arguments. The key difference between this concept and {{lc|std::predicate}} is that it is applied to the type that {{tt|I}} references, rather than {{tt|I}} itself. | ||
| + | |||
| + | ===Defect reports=== | ||
| + | {{dr list begin}} | ||
| + | {{dr list item|paper=P2609R3|std=C++20|before=one of the requirements was defined in terms of {{c|std::iter_value_t<I>&}}<br>which mishandled projections resulting in incompatibility with predicate {{c|F&}}|after=defined in terms of {{c|/*indirect-value-t*/<I>}}<br>to correctly handle such projections}} | ||
| + | {{dr list item|paper=P2997R1|std=C++20|before={{tt|indirect_unary_predicate}} required {{c|F&}} to satisfy {{lconcept|predicate}} with<br>{{c|std::iter_common_reference_t<I>}}|after=does not require}} | ||
| + | {{dr list end}} | ||
{{langlinks|es|ja|zh}} | {{langlinks|es|ja|zh}} | ||
Latest revision as of 17:59, 23 August 2024
| Defined in header <iterator>
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| template< class F, class I > concept indirect_unary_predicate = |
(since C++20) | |
The concept indirect_unary_predicate specifies requirements for algorithms that call unary predicates as their arguments. The key difference between this concept and std::predicate is that it is applied to the type that I references, rather than I itself.
[edit] Defect reports
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
| DR | Applied to | Behavior as published | Correct behavior |
|---|---|---|---|
| P2609R3 | C++20 | one of the requirements was defined in terms of std::iter_value_t<I>& which mishandled projections resulting in incompatibility with predicate F& |
defined in terms of /*indirect-value-t*/<I> to correctly handle such projections |
| P2997R1 | C++20 | indirect_unary_predicate required F& to satisfy predicate withstd::iter_common_reference_t<I> |
does not require |
