fact: Fixpoint wder_sigma (r1 r2: regular_expression) (s t: word char) : regular_expression := match t with | [::] => Conc (wder s r1) r2 | hd :: tl => if has_eps (wder s r1) then Plus (wder_sigma r1 r2 (s ++ [:: hd]) tl) (wder t r2) else wder_sigma r1 r2 (s ++ [:: hd]) tl end.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq fintype) mathcomp(bigop path) RegLang(languages) RegexpBrzozowski(glue)