proposition: Lemma remove_nonterminal_4 {ls ps ps'} (H0 : is_valid_nonterminal (remove_nonterminal ls ps) ps') : ps <> ps'.
proof: Proof. intro H'. pose proof (proj2 (remove_nonterminal_2 ls _ _) (or_intror H')). congruence. Qed.
imports: Fiat.Common.Coq__8_4__8_5__Compat Coq.Classes.RelationClasses Coq.Setoids.Setoid Coq.ZArith.ZArith Fiat.Parsers.ContextFreeGrammar.Core Fiat.Parsers.BaseTypes