darcs patch: add Data.Set.notMember and Data.Map.notMember

[John Meacham]

On Thu, Mar 09, 2006 at 11:09:50PM +0100, Jean-Philippe Bernardy wrote:
> Hello,
> 
> Maybe I missed something, but are these two worth a name?
> 
> For reference:
> notMember k m = not $ member k m,
> in pointless style:
> notMember = (not .) . member
> 
> Any evidence to add to the case ?

* symmetry with elem/notElem

* quite useful for cleaning up guards:

f x | not (x `Set.member` map) && foo = ...
is hard to read.

* only a single obvious interpretation of meaning so people likely to
  define their own with same name conflicting with each other and it
  won't hurt to provide them.

* I likes em.

        John

-- 
John Meacham - ⑆repetae.net⑆john⑈