proposition: Lemma rmorphV : {in unit, {morph f: x / x^-1}}.
proof: Proof. move=> x Ux; rewrite /= -[(f x)^-1]mul1r. by apply: (canRL (mulrK (rmorph_unit Ux))); rewrite -rmorphM mulVr ?rmorph1. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div seq) mathcomp(choice fintype finfun bigop prime binomial)