let is_set num i =
  if i < 0 then
    failwith "Invalid bit index."
  else
    (num lsr i) land 0b00000001 <> 0

let two_complement n =
  (lnot n) + 1

let signed_byte n =
  if n land 0x80 <> 0 then -((two_complement n) land 0xFF)
  else n