proposition: Lemma size_inscode c i : size (inscode c i) = size c.
proof: Proof. Proof using. elim: c i => [| c0 c IHc] //= i. case: ltnP => _ /=; first by rewrite IHc. case: eqP => _ //=. by case: eqP => _ //=; rewrite IHc. Qed.
imports: HB(structures) mathcomp(all_ssreflect) mathcomp(fingroup perm morphism presentation) mathcomp(ssralg poly ssrint) permcomp tools permuted combclass congr