std::experimental::ranges::Relation

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)) is R,
• t, an expression such that decltype((t)) is T,
• u, an expression such that decltype((u)) is U,

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))).