template
<
class F, class I1, class I2 = I1 >
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
<F&, std::iter_reference_t
<I1>, std::iter_reference_t
<I2>>
;
|
|
(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
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 with
std::iter_common_reference_t<I>
|
does not require
|