binäre boolesche Operation f (n1, n2):
mit s(ni) = (li, xi, ri)
f (n1, n2) = f (¬x∧l1∨x∧r1,¬x∧l2∨x∧r2) = ¬x∧(f (l1, l2))∨x∧(f (r1, r2))
f (n1, n2) = f (¬x∧l1∨x∧r1, n2) = ¬x∧(f (l1, n2))∨x∧(f (r1, n2)).