Definition pures_same phi1 phi2 := forall loc k pp, phi1 @ loc = PURE k pp <-> phi2 @ loc = PURE k pp.

Lemma jsafeN_downward {Z} {Jspec : juicy_ext_spec Z} {ge n z c jm} :
jsafeN Jspec ge (S n) z c jm ->
jsafeN Jspec ge n z c jm.