proposition: Lemma flip_lt_negate_r x y : y < - x -> x < - y.
proof: Proof. pattern y at 1. rewrite <- (@involutive _ (-) _ y). apply flip_lt_negate. Qed.
imports: HoTT.Classes.interfaces.abstract_algebra HoTT.Classes.interfaces.orders HoTT.Classes.theory.groups HoTT.Classes.theory.rings HoTT.Classes.orders.semirings