proposition: Lemma positive_to_nonterminal_eq_iff_l x y : positive_to_nonterminal x = y <-> x = nonterminal_to_positive y.
proof: Proof. rewrite <- positive_to_nonterminal_eq, nonterminal_to_positive_to_nonterminal; reflexivity. Qed.
imports: Coq.PArith.BinPos Coq.PArith.Pnat Coq.Arith.Arith Coq.FSets.FMapInterface Coq.FSets.FMapPositive Fiat.Parsers.ContextFreeGrammar.Carriers Fiat.Common.List.ListFacts Fiat.Common.List.ListMorphisms Fiat.Common.Prod