Definition reducts_incl {A B: Type} (C: A -> B) (res1: reducts A) (res2: reducts B) : Prop :=
  forall C1 rd, In (C1, rd) res1 -> In ((fun x => C(C1 x)), rd) res2.

Lemma not_imm_safe_stuck_red: forall m a k C, context k RV C -> ~imm_safe_t k a m -> exists C', In (C', Stuckred) (step_expr RV (C a) m).