std::strict_weak_order
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strict_weak_order
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Defined in header
<concepts>
template< class R, class T, class U >
concept strict_weak_order = std::relation <R, T, U>;
(since C++20)
concept strict_weak_order = std::relation <R, T, U>;
The concept strict_weak_order<R, T, U> specifies that the relation R imposes a strict weak ordering on its arguments.
[edit] Semantic requirements
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.
[edit] Notes
The distinction between relation and strict_weak_order is purely semantic.
[edit] References
- C++23 standard (ISO/IEC 14882:2024):
- 18.7.7 Concept
strict_weak_order[concept.strictweakorder]
- 18.7.7 Concept
- C++20 standard (ISO/IEC 14882:2020):
- 18.7.7 Concept
strict_weak_order[concept.strictweakorder]
- 18.7.7 Concept