[Haskell-beginners] error monad and Map lookup

[Brandon Allbery]

On Thu, Dec 22, 2011 at 14:44, Dennis Raddle <dennis.raddle at gmail.com>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

-- 
brandon s allbery                                      allbery.b at gmail.com
wandering unix systems administrator (available)     (412) 475-9364 vm/sms
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