fact: Variable (X : Type) (P : X -> Prop) (Pdec : forall x, { P x } + { ~ P x }).
imports: List Arith Lia Eqdep_dec Bool Undecidability.Shared.Libs.DLW.Utils(utils_tac utils_list utils_nat) Undecidability.Shared.Libs.DLW.Vec(pos vec)