std::equivalence_relation

 

C++

Compiler support

Freestanding and hosted

Language

Standard library headers

Named requirements

Feature test macros (C++20)

Language support library

Concepts library (C++20)

Diagnostics library

General utilities library

Strings library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Numerics library

Localizations library

Input/output library

Filesystem library (C++17)

Regular expressions library (C++11)

Atomic operations library (C++11)

Thread support library (C++11)

Technical specifications

Symbols index

External libraries

 

Concepts library

Core language concepts same_as derived_from convertible_to common_reference_with common_with integral signed_integral unsigned_integral floating_point swappableswappable_with destructible constructible_from default_initializable move_constructible copy_constructible assignable_from

Comparison concepts equality_comparableequality_comparable_with totally_orderedtotally_ordered_with Object concepts movable copyable semiregular regular Callable concepts invocableregular_invocable predicate relation equivalence_relation strict_weak_order

 

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.

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).

Notes

The distinction between relation and equivalence_relation is purely semantic.