[Haskell-beginners] type of pattern matching

[Michael Mossey]

David Virebayre wrote:
> On Wed, Jul 7, 2010 at 9:19 AM, Michael Mossey <mpm at alumni.caltech.edu> 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