proposition: Lemma in_CAll : forall u, (u \in CNot CVoid).
proof: Proof. move => u; rewrite -topredE /= /mem_creg /=. by apply/negP. Qed.
imports: Coq(RelationClasses Setoid Morphisms) HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq fintype) mathcomp(bigop path) RegLang(languages) RegexpBrzozowski(glue regexp finite_der equiv)