Re: new MonadRandom instance; and maintainership

Uhm, yeah, I forgot that you can still use monadic bind together with the Alternative methods. Never mind me! Sjoerd On Apr 26, 2013, at 12:22 AM, Felipe Almeida Lessa wrote:

Wouldn't Alternative lead to the same bug?

On Thu, Apr 25, 2013 at 7:02 PM, Sjoerd Visscher wrote:

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Maybe a derived Alternative instance for RandT still makes sense?

Sjoerd

On Apr 25, 2013, at 8:28 PM, Brent Yorgey wrote:

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On Thu, Apr 25, 2013 at 10:47:57AM -0400, Brent Yorgey wrote:

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On Wed, Apr 24, 2013 at 02:38:01PM -0400, Brent Yorgey wrote:

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Hi all,

I would like to add a derived MonadPlus instance for both Rand and RandT. Also, since it seems that MonadRandom has no maintainer I propose to take on its maintainership. Any comments/objections/etc. welcome.

Also, ignore what I said about deriving an instance for Rand, that does not make any sense. However, adding an instance for RandT does still make sense. A repository with the changes is here:

http://github.com/byorgey/MonadRandom

I'll upload in a few days if no one objects.

Puzzle time! Can you explain the semantics of the following code (given a derived MonadPlus instance for RandT)?

maybeFail :: RandT StdGen Maybe () maybeFail = do r <- getRandomR (0, 1 :: Double) guard (r < 1/2)

succeed :: RandT StdGen Maybe () succeed = maybeFail `mplus` succeed

I therefore rescind my proposal to add a MonadPlus instance for RandT. However, I still volunteer to be the maintainer. =)

-Brent

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-- Felipe.