std::StrictWeakOrder

C++

Language

Headers

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Named requirements

Language support library

Concepts library (C++20)

Diagnostics library

Utilities library

Strings library

Containers library

Algorithms library

Iterators library

Numerics library

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Regular expressions library (C++11)

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Technical Specifications

Concepts library

Core language concepts
Same DerivedFrom ConvertibleTo CommonReference Common	Integral SignedIntegral UnsignedIntegral Assignable SwappableSwappableWith	Destructible Constructible DefaultConstructible MoveConstructible CopyConstructible
Comparison concepts
Boolean	EqualityComparableEqualityComparableWith	StrictTotallyOrderedStrictTotallyOrderedWith
Object concepts
Movable Copyable	Semiregular Regular
Callable concepts
InvocableRegularInvocable	Predicate	Relation StrictWeakOrder

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

The concept StrictWeakOrder<R, T, U> specifies that the Relation R imposes a strict weak ordering on its arguments. A relation r is a strict weak ordering if

• it is irreflexive: for all x, r(x, x) is false;
• it is transitive: for all a, b and c, if r(a, b) and r(b, c) are both true then r(a, c) is true;
• let e(a, b) be !r(a, b) &&!r(b, a), then e is transitive: e(a, b) && e(b, c) implies e(a, c).

Under these conditions, it can be shown that e is an equivalence relation, and r induces a strict total ordering on the equivalence classes determined by e.

Notes

The distinction between Relation and StrictWeakOrder is purely semantic.