fact: Definition test := (fun x n => match f n with Some y => d x y | None => false end).
imports: Undecidability.L(Computability.MuRec) Undecidability.L.Datatypes(LNat LOptions LProd) Undecidability.Synthetic(DecidabilityFacts EnumerabilityFacts ListEnumerabilityFacts ReducibilityFacts) Undecidability.L.Datatypes.List(List_basics List_nat) Datatypes