std::experimental::ranges::Relation
|   Defined in header  <experimental/ranges/concepts>
  | 
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|   template< class R, class T, class U > concept bool Relation =  | 
(1) | (ranges TS) | 
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.
Given
-  
r, an expression such that decltype((r)) isR, -  
t, an expression such that decltype((t)) isT, -  
u, an expression such that decltype((u)) isU, 
and let C be ranges::common_reference_t<const std::remove_reference_t<T>&, const std::remove_reference_t<U>&>,
then Relation<R, T, U> is satisfied only if
- bool(r(t, u)) == bool(r(C(t), C(u))) and
 - bool(r(u, t)) == bool(r(C(u), C(t))).