fact: Definition SUB (r1 r2: bregexp) := forall s, (s \in r1) -> (s \in r2).
imports: Coq(RelationClasses) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq fintype) mathcomp(bigop path) RegLang(languages) RegexpBrzozowski(glue gfinset regexp finite_der)