std::strict_weak_order
From cppreference.com
| Defined in header <concepts>
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| template< class R, class T, class U > concept strict_weak_order = std::relation<R, T, U>; |
(since C++20) | |
The concept strict_weak_order<R, T, U> specifies that the relation R imposes a strict weak ordering on its arguments.
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.
Notes
The distinction between relation and strict_weak_order is purely semantic.