| m < # buf, n0 < # buf, (buf[n0] = empty ⊃ datasize(buf, n0);n0 + 1) < datasize(buf, m), m ≤ n0, ¬ m < n0 ∨ ¬ datasize(buf, n0) < datasize(buf, m) ⊦ |
(buf[n0] = empty ⊃ datasize(buf, n0);n0 + 1) < datasize(buf, m), n0 < # buf, m < # buf, m ≤ n0 ⊦ m < n0
(buf[n0] = empty ⊃ datasize(buf, n0);n0 + 1) < datasize(buf, m), n0 < # buf, m < # buf, m ≤ n0 ⊦ datasize(buf, n0) < datasize(buf, m)