Re: [Haskell-cafe] nested maybes

4 Feb 2007


      On 2/4/07, Martin DeMello  wrote:
...
I have a Data.Map.Map String -> (Layout, [String]) as follows:
type Anagrams = [String]
type Cell = (Layout, Anagrams)
type WordMap = Map.Map String Cell
exists str wmap =
  let a = Map.lookup (sort str) wmap in
      case a of
           Nothing -> False
           Just x -> case (find (== str) (snd x)) of
                          Nothing -> False
                          _       -> True
the existence test looks ugly - any more compact way to write it?
How about:
exists str = fromMaybe False . fmap (elem str.snd) . Map.lookup (sort str)

-- 
Cheers,
  Lemmih