Difference between revisions of "cpp/iterator/indirect equivalence relation"
(apply DR20: P2609R3 Relaxing Ranges Just A Smidge (replace iter_value_t<I>& with indirect-value-t<I>)) |
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template< class F, class I1, class I2 = I1 > | template< class F, class I1, class I2 = I1 > | ||
concept indirect_equivalence_relation = | concept indirect_equivalence_relation = | ||
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<F&, std::iter_reference_t<I1>, std::iter_reference_t<I2>>; | <F&, std::iter_reference_t<I1>, std::iter_reference_t<I2>>; | ||
}} | }} | ||
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{{dcl end}} | {{dcl end}} | ||
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{{dr list begin}} | {{dr list begin}} | ||
{{dr list item|paper=P2609R3|std=C++20|before=some requirements were defined in terms of {{c|std::iter_value_t<I>&}}<br>which mishandled projections resulting in incompatibility with equivalence relation {{c|F&}}|after=defined in terms of {{c|/*indirect-value-t*/<I>}}<br>to correctly handle such projections}} | {{dr list item|paper=P2609R3|std=C++20|before=some requirements were defined in terms of {{c|std::iter_value_t<I>&}}<br>which mishandled projections resulting in incompatibility with equivalence relation {{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_equivalence_relation}} required {{c|F&}} to satisfy {{lconcept|equivalence_relation}} with<br>{{c|std::iter_common_reference_t<I>}}|after=does not require}} | ||
{{dr list end}} | {{dr list end}} | ||
{{langlinks|es|ja|zh}} | {{langlinks|es|ja|zh}} | ||
Latest revision as of 18:07, 23 August 2024
| Defined in header <iterator>
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| template< class F, class I1, class I2 = I1 > concept indirect_equivalence_relation = |
(since C++20) | |
The concept indirect_equivalence_relation specifies requirements for algorithms that call equivalence relations as their arguments. The key difference between this concept and std::equivalence_relation is that it is applied to the types that I1 and I2 references, rather than I1 and I2 themselves.
[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 | some requirements were defined in terms of std::iter_value_t<I>& which mishandled projections resulting in incompatibility with equivalence relation F& |
defined in terms of /*indirect-value-t*/<I> to correctly handle such projections |
| P2997R1 | C++20 | indirect_equivalence_relation required F& to satisfy equivalence_relation withstd::iter_common_reference_t<I> |
does not require |
