| ⊦ bnode(rp, zbrar, m, len, nused, height + 1, dirty, ri, iast, as, alladrs) = ( ⌜m + len ≤ nused ∧ nused ≤ # zbrar ∧ # zbrar = BRANCH_SIZE⌝ ∧ ⌜nused ≠ 0 ∧ sorted(zbrar, 0, nused - 1)⌝ ∧ _∃ (λ asar. _∃ (λ asar0. ⌜ # asar = nused ∧ disj(asar, 0, nused) ∧ union(asar, m, len) = as ∧ # asar0 = nused ∧ disj(asar0, 0, nused) ∧ union(asar0, m, len) = alladrs ⌝ ∧ (λ n. ⌜zbrar[n].branch?⌝ ∧ btree(rp, zbrar[n].child, zbrar[n].adr, height, dirty, key-range(zbrar, n, nused, ri), iast, asar[n], asar0[n], ok) )⊗_ (m, len )))) |