proposition: Lemma PlusVoid : forall c, c =i Plus c Void.
proof: Proof. move => c x. rewrite -[_ \in Plus _ _]topredE /=. apply/idP/orP; first by move => h; left. by case. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq fintype) mathcomp(bigop path) RegLang(languages) RegexpBrzozowski(glue)