proposition: Lemma first_char_in_nil (str : String) : first_char_in str nil <-> length str = 0.
proof: Proof. unfold first_char_in. split. { eapply for_first_char_False; simpl; eauto. } { apply for_first_char_nil. } Qed.
imports: Fiat.Common.Coq__8_4__8_5__Compat Coq.ZArith.ZArith Fiat.Parsers.StringLike.Core Fiat.Parsers.StringLike.Properties Fiat.Parsers.StringLike.ForallChars Fiat.Common