proposition: Lemma in_igotos_unique_index {i i' n X Y} : In (i, (n, X, Y)) igotos -> In (i', (n, X, Y)) igotos -> i = i'.
proof: Proof. by move=> /nth_error_Some_In_combineP /gotos_indexP + /nth_error_Some_In_combineP /gotos_indexP => <-. 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