darcs patch: Add justIf to Data.Maybe

[Joachim Breitner]

Hi,

Am Samstag, den 22.08.2009, 10:13 +0100 schrieb Jon Fairbairn:
> Joachim Breitner <mail at joachim-breitner.de> writes:
> > I propose the attached change, with a discussion timeframe until end of
> > September. The corresponding ticket is
> > http://hackage.haskell.org/trac/ghc/ticket/3446
> >
> > Thanks,
> > Joachim
> 
> I have been meaning to get round to proposing check for Data.Monad:
> 
> > check :: (MonadPlus m) => (a -> Bool) -> a -> m a
> > check p a
> >     | p a = return a
> >     | otherwise = mzero
> 
> Now justIf = flip (check . const)
> 
> So I suggest that it would be better to add check first(, and then
> possibly switch the order of arguments to justIf).

are you proposing that, if check is available, no justIf is needed in
the libraries? Or are you just proposing a different implementation?

Greetings,
Joachim

-- 
Joachim Breitner
  e-Mail: mail at joachim-breitner.de
  Homepage: http://www.joachim-breitner.de
  ICQ#: 74513189
  Jabber-ID: nomeata at joachim-breitner.de
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