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std::indirect_equivalence_relation

Defined in header <iterator> 
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&, std::iter_value_t<I1>&, std::iter_value_t<I2>&> &&
  std::equivalence_relation<F&, std::iter_value_t<I1>&, std::iter_reference_t<I2>> &&
  std::equivalence_relation<F&, std::iter_reference_t<I1>, std::iter_value_t<I2>&> &&
  std::equivalence_relation<F&, std::iter_reference_t<I1>, std::iter_reference_t<I2>> &&
  std::equivalence_relation<F&, std::iter_common_reference_t<I1>, std::iter_common_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 themselves.

Semantic requirements

F, I1, and I2 model indirect_equivalence_relation only if all concepts it subsumes are modeled.

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