Re: darcs patch: Add justIf to Data.Maybe

Joachim Breitner writes:

Hi,

Am Samstag, den 22.08.2009, 10:13 +0100 schrieb Jon Fairbairn:

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Joachim Breitner writes:

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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:

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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?

I wouldn't be proposing that, having promised not to post on the topic of naming short functions for ten years.

Or are you just proposing a different implementation?

I /am/ proposing that. I suppose I have to work out how to make a proper proposal for the addition of check? -- Jón Fairbairn Jon.Fairbairn@cl.cam.ac.uk