std::equivalence_relation
Min standard notice:
Header: <concepts>
The concept equivalence_relation<R, T, U> specifies that the relation R imposes an equivalence relation on its arguments.
# Declarations
template< class R, class T, class U >
concept equivalence_relation = std::relation<R, T, U>;
(since C++20)
# Notes
The distinction between relation and equivalence_relation is purely semantic.