proposition: Lemma cat_bseqP s (s' : m.-bseq T) : size (s ++ s') <= n + m.
proof: Proof. by rewrite size_cat; apply/leq_add/size_bseq/size_bseq. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat) mathcomp(seq choice fintype path)