0 ≤ i ⊦ i→n(i) < m ↔ i < n→i(m)
Used simplifier rules: ⊦ ~1 < i ↔ 0 ≤ i; (s)%numlef-01: ⊦ (* i) ≤ j → i - 1 < j; (forward) from specification int-abs