std::equivalence_relation
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equivalence_relation
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Exposition-only concepts
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Defined in header
<concepts>
template< class R, class T, class U >
concept equivalence_relation = std::relation <R, T, U>;
(since C++20)
concept equivalence_relation = std::relation <R, T, U>;
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
aandb,r(a, b)is true if and only ifr(b, a)is true; - it is transitive:
r(a, b) && r(b, c)impliesr(a, c).
[edit] Notes
The distinction between relation and equivalence_relation is purely semantic.
[edit] References
- C++23 standard (ISO/IEC 14882:2024):
- 18.7.6 Concept
equivalence_relation[concept.equiv]
- 18.7.6 Concept
- C++20 standard (ISO/IEC 14882:2020):
- 18.7.6 Concept
equivalence_relation[concept.equiv]
- 18.7.6 Concept