fact: Definition bregexp_sub (r1 r2:bregexp) := bregexp_eq r2 (Plus r1 r2).
imports: Coq(RelationClasses) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq fintype) mathcomp(bigop path) RegLang(languages) RegexpBrzozowski(glue gfinset regexp finite_der)