| n + 1 = datasize(buf, n2), buf[n2] = empty, datasize(buf, n) = datasize(buf, n2), n < # buf, n < n0, n < n2, n0 ≤ n2, datasize(buf, n2) ≤ # buf, datasize(buf, n2) ≤ n0, datasize(buf, n2) ≤ n2, ∀ n1. n ≤ n1 ∧ ¬ n2 < n1 → buf[n1] = empty ⊦ datasize(buf, n) = datasize(buf, n2) ↔ (∀ n3. n ≤ n3 ∧ n3 < n2 → buf[n3] = empty), buf[n] = empty, buf[n0] = empty |
n + 1 = datasize(buf, n2), buf[n2] = empty, datasize(buf, n) = datasize(buf, n2), n < n2, n < n0, n < # buf, n1 < n2, datasize(buf, n2) ≤ n2, datasize(buf, n2) ≤ n0, datasize(buf, n2) ≤ # buf, n0 ≤ n2, n ≤ n1, ∀ n1. n ≤ n1 ∧ ¬ n2 < n1 → buf[n1] = empty ⊦ buf[n0] = empty, buf[n] = empty, buf[n1] = empty