fact: Fixpoint list_prod X Y (l : list X) (m : list Y) := match l with | nil => nil | x::l => map (fun y => (x,y)) m ++ list_prod l m end.
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)