fact: Variable similar_PlusA : forall c1 c2 c3, similar (Plus (Plus c1 c2) c3) (Plus c1 (Plus c2 c3)).
imports: Coq(RelationClasses) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq fintype) mathcomp(bigop path) RegLang(languages) RegexpBrzozowski(glue gfinset regexp finite_der)