fact: Variable Y_fresh : Forall (fun '((_, _, x), (_, _, y)) => x <> Y /\ y <> Y) M.
imports: Relation_Operators Operators_Properties List Lia PeanoNat Undecidability.StackMachines.SMN Undecidability.StackMachines.Util(List_facts SMN_facts) ssreflect ssrbool ssrfun