proposition: Lemma universal_maybe_reachable_terminal {x T} : (forall z, maybe_reachable T x z) -> exists y, reachable_n T x y /\ terminal M y.
proof: Proof. move=> /(_ ([], [], '?|)). case; last done. move=> ?. eexists. constructor; first by eassumption. by move=> ? /bound_try_step_shape [? ?]. Qed.
imports: Relation_Operators Operators_Properties Lia PeanoNat List Undecidability.StackMachines.Reductions.CM1_HALT_to_SMNdl_UB.SMX_facts Undecidability.StackMachines.Util(Nat_facts List_facts) ssreflect ssrbool ssrfun