std::indirect_binary_predicate
Defined in header <iterator> | ||
|---|---|---|
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.
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 |
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