law zbk_byte

lawful-bytes@0.1.1.0 · proof_fast_w1.bend:62

import Base
import lawful-words@0.1.0.0/proof_zb.bend as Z

62# With no borrow in and the byte's flag kept by the mask, the masked flags are
63# all clear exactly when the byte is not zero and the rest are clear.
64law zbk_byte:
65  for +n: Nat
66  for +x: Word(8n)
67  for +r: Word(n)
68  for +kr: Word(n)
69  for +hr: Word(n)
70  for +mr: Word(n)
71  {Z.allz(Nat.add(8n, n), Word.and(Nat.add(8n, n), Z.zf(Nat.add(8n, n), Z.app8(n, x, r), Z.app8(n, Z.one8(), kr), Z.app8(n, Z.h8(), hr), True{}), Z.app8(n, Z.h8(), mr)))
72    == Bool.and(Bool.not(Z.allz(8n, x)), Z.allz(n, Word.and(n, Z.zf(n, r, kr, hr, True{}), mr))) : Bool}