new MonadRandom instance; and maintainership

[Sjoerd Visscher]

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 <felipe.lessa at gmail.com> wrote:

> Wouldn't Alternative lead to the same bug?
> 
> On Thu, Apr 25, 2013 at 7:02 PM, Sjoerd Visscher <sjoerd at w3future.com> wrote:
>> Maybe a derived Alternative instance for RandT still makes sense?
>> 
>> Sjoerd
>> 
>> On Apr 25, 2013, at 8:28 PM, Brent Yorgey <byorgey at seas.upenn.edu> wrote:
>> 
>>> On Thu, Apr 25, 2013 at 10:47:57AM -0400, Brent Yorgey wrote:
>>>> On Wed, Apr 24, 2013 at 02:38:01PM -0400, Brent Yorgey wrote:
>>>>> 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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>> 
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> 
> 
> -- 
> Felipe.