proposition: Lemma index_no_step_shape {y l r i} : SMX.step M (l, r, '#-i) y -> (r = [§0] ++ skipn 1 r).
proof: Proof. by move /stepE => [] > [] *; subst. 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