Re: Proposal: Move 'split' into a separate class in System.Random

15 Sep 2010


      On Wed, Sep 15, 2010 at 05:41:19PM +0100, Duncan Coutts wrote:
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On 15 September 2010 17:08, Thomas DuBuisson  wrote:
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On Wed, Sep 15, 2010 at 7:57 AM, Ian Lynagh  wrote:
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I approve, but what do you propose to do for haskell98:Random?
Someone (me?) should make a matching proposal to Haskell' once we have
decided on a reasonable way forward.  WRT H98, modifying the Haskell98
library to have an upper bound on random 1.0.x would make sense.
Having two incompatible classes is rather inescapable when one is in a
standard and the other is its replacement.
Right, if we change the class then we do necessarily make it
incompatible with H98, so H98 will have to have its own definition of
Random that does not share type or class definitions with the random
package.
I think at that point having the haskell98 package depend on the
random package at all makes little sense. We would just take a copy of
the old H98 code and put that in the H98 package.
Right. In particular, we need to be able to build haskell98 as part of
GHC, and it would be a lot simpler not to have 2 versions of the random
library around.
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Henning said:
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class StraightRandomGen g where
 System.Random.next :: g -> (Int, g)
 System.Random.genRange :: g -> (Int, Int)
class StraightRandomGen g => RandomGen g where
I favor a clean break with the past and small flurry of fixing
activity. The more concessions made in the base libraries the odder
all libraries will feel.
I agree. As much as possible I think we should deal with API changes
using package versioning and not by making more convoluted names.
I agree too. The short-term pain for those who need to update their code
to include a Splittable constraint is preferable to the long-term pain
of living with the suboptimal names, IMO.


Thanks
Ian