fact: Definition first_char_in__iff__for_first_char' {str ls} {P : _ -> Prop} (H : forall ch, P ch <-> List.In ch ls) : first_char_in str ls <-> for_first_char str P.
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