-module Bit where
+-- | The Bit module contains the Bit data type, which is essentially a
+-- renamed Boolean, and some convenience functions.
+module Bit
+where
+
+import Test.QuickCheck (
+ Arbitrary,
+ arbitrary,
+ elements
+ )
+
data Bit = Zero | One
- deriving (Eq, Show)
+ deriving (Eq)
+
+instance Show Bit where
+ show Zero = "0"
+ show One = "1"
+
+instance Arbitrary Bit where
+ arbitrary = elements [ Zero, One ]
+
+
+-- | Convert a Bit to an Int.
bit_to_int :: Bit -> Int
-bit_to_int Zero = 0
-bit_to_int One = 1
-
--- If we are passed a '0' or '1', convert it appropriately. Otherwise,
--- default to Zero.
-bit_from_char :: Char -> Bit
-bit_from_char '0' = Zero
-bit_from_char '1' = One
-bit_from_char _ = Zero
+bit_to_int Zero = 0
+bit_to_int One = 1
+
+-- | If we are passed a '0' or '1', convert it
+-- appropriately. Otherwise, return Nothing.
+bit_from_char :: Char -> Maybe Bit
+bit_from_char '0' = Just Zero
+bit_from_char '1' = Just One
+bit_from_char _ = Nothing