fact: Fixpoint Prefix_dec {X_eq : X -> X -> Prop} (X_eq_dec : forall x x', {X_eq x x'} + {~ X_eq x x'}) {X_refl : Reflexive X_eq} (p s : list X) : {Prefix X_eq p s} + {~ Prefix X_eq p s}.
imports: Coq.Lists.SetoidList Fiat.QueryStructure.Specification.Representation.QueryStructureNotations