fact: Fixpoint fo_term_vars t := match t with | in_var x => x::nil | @in_fot s v => concat (vec_list (vec_map fo_term_vars v)) end.
imports: List Arith Lia Eqdep_dec Undecidability.Shared.Libs.DLW.Utils(utils_tac utils_list utils_nat finite) Undecidability.Shared.Libs.DLW.Vec(pos vec) Undecidability.FOL.TRAKHTENBROT(notations utils decidable fol_ops fo_sig)