fact: Definition ff (r1 r2:bregexp) (efw:bregexp*bregexp*bword) := let (ef,w) := efw in let (e,f) := ef in (wder (rev w) r1) ≡ e /\ (wder (rev w) r2) ≡ f.
imports: Coq(RelationClasses) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq fintype) mathcomp(bigop path) RegLang(languages) RegexpBrzozowski(glue gfinset regexp finite_der)