X-Git-Url: http://gitweb.michael.orlitzky.com/?a=blobdiff_plain;f=src%2FBit.hs;h=e3d90e420e2bffbbe97accd2ad08246731aacde4;hb=942b8ef3bc5830ca0defa62342d55550aea59934;hp=7c1840823b041774774f7d49519ff190f6f52033;hpb=5825a18ea1267c1f769a054c650b2761de7f291c;p=hath.git

diff --git a/src/Bit.hs b/src/Bit.hs
index 7c18408..e3d90e4 100644
--- a/src/Bit.hs
+++ b/src/Bit.hs
@@ -1,16 +1,46 @@
-module Bit where
+-- | The Bit module contains the Bit data type, which is essentially a
+--   renamed Boolean, and some convenience functions.
+module Bit
+where
 
-data Bit = None | Zero | One
-         deriving (Eq, Show)
+import Test.QuickCheck (
+  Arbitrary,
+  arbitrary,
+  elements
+  )
 
+
+data Bit = Zero | One
+  deriving (Enum, Eq)
+
+instance Show Bit where
+  show Zero = "0"
+  show One  = "1"
+
+
+instance Arbitrary Bit where
+  arbitrary = elements [ Zero, One ]
+
+
+instance Ord Bit where
+  Zero <= Zero = True
+  Zero <= One  = True
+  One  <= Zero = False
+  One  <= One  = True
+
+instance Bounded Bit where
+  minBound = Zero
+  maxBound = One
+
+
+-- | Convert a Bit to an Int.
 bit_to_int :: Bit -> Int
-bit_to_int None = -1
 bit_to_int Zero =  0
 bit_to_int One  =  1
 
--- If we are passed a '0' or '1', convert it appropriately. Otherwise,
--- default to None.
-bit_from_char :: Char -> Bit
-bit_from_char '0' = Zero
-bit_from_char '1' = One
-bit_from_char  _  = None
+-- | 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