darcs patch: Add justIf to Data.Maybe
duncan.coutts at worc.ox.ac.uk
Wed Aug 26 17:16:24 EDT 2009
On Wed, 2009-08-26 at 18:58 +0100, Jon Fairbairn wrote:
> > It's not that hard to write
> > all_spaces xs = checkA (all (isSpace xs)) xs
> > if that's really what you want.
> Not /hard/, but it involves using xs twice, which should tell us
I'm not sure it does tell us much, given that there are also cases where
we need to use it only once, and would be forced to use \_ -> to ignore
it in the predicate.
The two forms are clearly inter-convertible and one form is more
convenient in some situations while the other is more convenient in
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