std::relation

 

C++

Compiler support

Freestanding and hosted

Language

Standard library

Standard library headers

Named requirements

Feature test macros(C++20)

Language support library

Concepts library(C++20)

Diagnostics library

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Metaprogramming library(C++11)

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Containers library

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Ranges library(C++20)

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Filesystem library(C++17)

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Technical specifications

Symbols index

External libraries

 

Concepts library

Core language concepts same_as (C++20) derived_from (C++20) convertible_to (C++20) common_reference_with (C++20) common_with (C++20) integral (C++20) signed_integral (C++20) unsigned_integral (C++20) floating_point (C++20) swappableswappable_with (C++20)(C++20) destructible (C++20) constructible_from (C++20) default_initializable (C++20)   move_constructible (C++20) copy_constructible (C++20) assignable_from (C++20)

Comparison concepts equality_comparableequality_comparable_with (C++20)(C++20) totally_orderedtotally_ordered_with (C++20)(C++20) Object concepts movable (C++20) copyable (C++20) semiregular (C++20) regular (C++20) Callable concepts invocableregular_invocable (C++20)(C++20) predicate (C++20) relation (C++20) equivalence_relation (C++20) strict_weak_order (C++20)

Exposition-only concepts boolean-testable  (C++20)

 

Defined in header <concepts>
template<class R, class T, class U > concept relation =     std::predicate<R, T, T>&&std::predicate<R, U, U>&&     std::predicate<R, T, U>&&std::predicate<R, U, T>;	(1)	(since C++20)

The concept relation<R, T, U> specifies that R defines a binary relation over the set of expressions whose type and value category are those encoded by either T or U.

References

• C++23 standard (ISO/IEC 14882:2024):

• 18.7.5 Concept relation [concept.relation]

• C++20 standard (ISO/IEC 14882:2020):

• 18.7.5 Concept relation [concept.relation]