proposition: Lemma mem_wder : forall s e, mem_der e s = has_eps (wder s e).
proof: Proof. by elim => /=. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq fintype) mathcomp(bigop path) RegLang(languages) RegexpBrzozowski(glue)