Program Definition agedfrom {A} `{ageable A} (x:A) : pred A := necR x.

(* Specifications: *)
Lemma safe_approx : forall t t' p n r r' s s', level p < n -> termMeasure_incr t t' -> store_incr r r' -> stack_approx_rel n s s' -> safe t p r s -> safe t' p r' s'.
Lemma ev_halts_approx : forall t t' p n r r' s s', level p < n -> termMeasure_incr t t' -> store_incr r r' -> stack_approx_rel n s s' -> eventually_halts t p r s -> eventually_halts t' p r' s'.