std::indirect_binary_predicate - cppreference.com (original) (raw)
| | | | | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | ------------- | | template< class F, class I1, class I2 > concept indirect_binary_predicate = std::indirectly_readable<I1> && std::indirectly_readable<I2> && std::copy_constructible<F> && std::predicate<F&, /*indirect-value-t*/<I1>, /*indirect-value-t*/<I2>> && std::predicate<F&, /*indirect-value-t*/<I1>, std::iter_reference_t<I2>> && std::predicate<F&, std::iter_reference_t<I1>, /*indirect-value-t*/<I2>> && std::predicate<F&, std::iter_reference_t<I1>, std::iter_reference_t<I2>>; | | (since C++20) |
The concept indirect_binary_predicate
specifies requirements for algorithms that call binary predicates as their arguments. The key difference between this concept and std::predicate 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 predicate F& | defined in terms of /*indirect-value-t*/<I>to correctly handle such projections |
P2997R1 | C++20 | indirect_binary_predicate required F& to satisfy predicate withstd::iter_common_reference_t<I> | does not require |