darcs patch: Add justIf to Data.Maybe
Duncan Coutts
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
> something.
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
others.
Duncan
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