Re: [Haskell-beginners] error monad and Map lookup

On Thu, Dec 22, 2011 at 14:44, Dennis Raddle wrote:

test :: Int -> Either String String test x = do y <- case M.lookup x testMap of Nothing -> throwError "not in map" Just z -> return z return y

test x = maybe (Left "not in map") Right $ M.lookup x testMap

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