fact: Fixpoint R (X : seq A) (x y : A) := if X isn't z :: X' then R0 x y else Plus (Conc (R X' x z) (Conc (Star (R X' z z)) (R X' z y))) (R X' x y).
imports: HB(structures) mathcomp(all_ssreflect) RegLang(setoid_leq misc languages dfa nfa)