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std::equivalence_relation

From cppreference.com
< cpp‎ | concepts
Defined in header <concepts>
template < class R, class T, class U >
concept equivalence_relation = std::relation<R, T, U>;
(since C++20)

The concept equivalence_relation<R, T, U> specifies that the relation R imposes an equivalence relation on its arguments.

[edit] Semantic requirements

A relation r is an equivalence relation if

  • it is reflexive: for all x, r(x, x) is true;
  • it is symmetric: for all a and b, r(a, b) is true if and only if r(b, a) is true;
  • it is transitive: r(a, b) && r(b, c) implies r(a, c).

[edit] Notes

The distinction between relation and equivalence_relation is purely semantic.