fact: Definition step (c d : nfa2_config) := let: ((p,i),(q,j)) := (c,d) in ((q,R) \in read p i) && (j == i.+1 :> nat) || ((q,L) \in read p i) && (j.+1 == i :> nat).
imports: mathcomp(all_ssreflect) RegLang(misc languages dfa regexp myhill_nerode)