Re: [Haskell-beginners] type of pattern matching

7 Jul 2010


      David Virebayre wrote:
...
On Wed, Jul 7, 2010 at 9:19 AM, Michael Mossey  wrote:
...
doSomething :: Maybe Result
doSomething item = case item of
 note@(Note _ _ _ _ _) -> Just $ process note
 _                     ->  Nothing
But I don't like writing "Note _ _ _ _ _"
isNote (Note _ _ _ _ _) = True
isNote _                = False
doSomething :: Maybe Result
doSomething item | isNote item = Just $ process note
                 | otherwise   =  Nothing
But I don't like writing "Note _ _ _ _ _"
I think this is pretty good because I can use isNote with a filter in 
another function.

Thanks,
Mike