proposition: Lemma val_unitM x y : val (x * y : unit_of)%g = val x * val y.
proof: Proof. by []. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype finset fingroup morphism perm action) mathcomp(ssralg countalg)