module Main where

data BF = Zero | One | Add BF BF | Mul BF BF | Not BF
  deriving (Show, Eq)

evaluate :: BF -> BF
evaluate Zero = Zero
evaluate One  = One
evaluate (Add x y) | (evaluate x == Zero) && (evaluate y == Zero) = Zero
                   | otherwise = One
evaluate (Mul x y) | (evaluate x == One) && (evaluate y == One) = One
                   | otherwise = Zero
evaluate (Not x) | evaluate x == Zero = One
                 | otherwise          = Zero

a, b, c :: BF
a =
  (Not
      (     ((Zero `Add` ((One `Mul` Zero) `Mul` Not (One))) `Mul` Zero)
      `Add` (((One `Add` Zero) `Mul` (Not One)) `Add` Zero)
      )
    )
    `Mul` ((Not One) `Add` One)
b = Not
  (     (Not (Not ((Not Zero) `Add` One)) `Mul` (Zero `Mul` (Not One)))
  `Add` ((Not ((Not Zero) `Add` One)) `Mul` (Not (Zero `Mul` (Not One))))
  )
c =
  ((One `Add` (Not One)) `Mul` (Zero `Add` (Not ((Not Zero) `Mul` One))))
    `Add` (     (Not ((Zero `Mul` (Not One)) `Add` ((Not Zero) `Mul` One)))
          `Mul` (Not (Zero `Mul` One))
          )

main :: IO ()
main = mapM_
  (\(s, f) ->
    putStrLn
      $  s
      ++ " = "
      ++ (show f)
      ++ "\nEvaluate "
      ++ s
      ++ ":\n"
      ++ (show $ evaluate f)
      ++ "\n\n"
  )
  [("a", a), ("b", b), ("c", c)]