99 Haskell Problems: Problem 13

gistfile1.hs

data Count = Multiple Int Char 
	     | Single Char 
	     deriving (Eq, Show)
			
encodeDirect :: [Char] -> [Count]
encodeDirect = map toCount . foldr encode []
	where 
		toCount (x, y) = case x of
				   1 -> Single y
				   _ -> Multiple x y
		encode x [] = [(1, x)]
		encode x (y@(a, b):ys)
			| b == x = (a+1, b):ys
			| otherwise = (1, x):y:ys