proposition: Corollary lengthME s t : length s + length t <= length (s * t) -> length (s * t) = length s + length t.
proof: Proof. by move=> H; apply anti_leq; rewrite H lengthM. Qed.
imports: HB(structures) mathcomp(all_ssreflect) mathcomp(fingroup perm morphism presentation) mathcomp(ssralg poly ssrint) permcomp tools permuted combclass congr