Haskell Quiz/Phone Number Words/Solution Jethr0

dictionary = map (map toUpper) ["haskell", "join", "the", "quiz"]

-- fetch all possible words represented by a string of consecutive digits
-- the results are checked against the dictionary
-- if no result is found, the original string is returned as possibility
allPoss xs = if null result then [xs] else result
    where result    = filter (`elem` dictionary) . mapM poss $ xs
          poss char = encodings!! digitToInt char
          encodings = ["0", "1", "ABC", "DEF", "GHI", "JKL", "MNO", "PQRS", "TUV", "WXYZ"]

splitThem [] = []
splitThem xs = y : rest
    where (y,ys) = break (not . isDigit) xs
          rest   = splitThem . dropWhile (not . isDigit) $ ys

-- > phoneNames "1.800.5646.843.4275355.7849"
-- ["1-800-JOIN-THE-HASKELL-QUIZ"]
phoneNames = map (concat . intersperse "-") . mapM allPoss . splitThem