std::indirect_equivalence_relation
<iterator>
concept indirect_equivalence_relation =
std::indirectly_readable <I1> &&
std::indirectly_readable <I2> &&
std::copy_constructible <F> &&
std::equivalence_relation
<F&, /*indirect-value-t*/<I1>, /*indirect-value-t*/<I2>> &&
std::equivalence_relation
<F&, /*indirect-value-t*/<I1>, std::iter_reference_t <I2>> &&
std::equivalence_relation
<F&, std::iter_reference_t <I1>, /*indirect-value-t*/<I2>> &&
std::equivalence_relation
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.
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 |