A-M baby

Task/Gray-code/Haskell/gray-code.hs

@@ -0,0 +1,28 @@
+module Main where
+
+main = mapM_ (putStrLn . flip grayconvstr 5) [0..31]
+
+-- Convert number to bit list, MSB first.  Second argument is minimum width.
+num2bin :: (Integral t) => t -> t -> [t]
+num2bin n w = num2bin' n w [] where
+  num2bin' n w acc | n <= 0 && w <= 0 = acc
+                   | otherwise = num2bin' m (w-1) (b:acc)
+    where (m, b) = divMod n 2
+
+xor2 :: (Integral t) => t -> t -> t
+xor2 x y = (x + y) `mod` 2
+
+bin2gray :: (Integral t) => [t] -> [t]
+bin2gray [] = []
+bin2gray (x:xs) = x : zipWith xor2 xs (x:xs)
+
+gray2bin :: (Integral t) => [t] -> [t]
+gray2bin = scanl1 xor2
+
+-- Prettyprinting, since it is in the task description...
+grayconvstr :: (Integral t, Show t) => t -> t -> String
+grayconvstr n w = (show n) ++ ": " ++ (show b) ++ " => " ++ (show g) ++ " => " ++ (show u)
+  where
+    b = num2bin n w
+    g = bin2gray b
+    u = gray2bin g