| n < nused, n < # zbrar, nused ≤ # zbrar ⊦ key-range(zbrar, n, nused, ri) = (n = 0 ⊃ (nused = 1 ⊃ ri;ri |≤ zbrar[0].key);(n + 1 = nused ⊃ ri |> zbrar[n - 1].key;(ri |> zbrar[n - 1].key) |≤ zbrar[n].key)) |
n = 0, n < # zbrar, n < nused, nused ≤ # zbrar ⊦ key-range(zbrar, n, nused, ri) = (nused = 1 ⊃ ri;ri |≤ zbrar[0].key)
n < # zbrar, n < nused, nused ≤ # zbrar ⊦ key-range(zbrar, n, nused, ri) = (n + 1 = nused ⊃ ri |> zbrar[n - 1].key;(ri |> zbrar[n - 1].key) |≤ zbrar[n].key), n = 0