Re: Monad Maybe?

"Russell O'Connor" writes:

[To: haskell-cafe@haskell.org]

Is there a nicer way of writing the following sort of code?

case (number g) of Just n -> Just (show n) Nothing -> case (fraction g) of Just n -> Just (show n) Nothing -> case (nimber g) of Just n -> Just ("*"++(show n)) Nothing -> Nothing

what about? listToMaybe $ mapMaybe (\ (f, format) -> fmap format (f g)) l where l = [ (number, show), (fraction, show), (nimber, (\ n -> "*" ++ show n)) ] or: if_just (number g) show $ if_just (fraction g) show $ if_just (nimber g) (\ n -> "*" ++ show n) Nothing using: if_just (Just e) f _ = Just(f e) if_just Nothing _ f = f