Enhancements to random number generators

[farrellm]

I'm thinking of coding up a few enhancements to the existing library support for random number generators but looking for some feedback and advice on where to put it.

1. Port System.Random from Haskell. This adds the RandomGen interface.
2. Should System.Random go in contrib for now?
3. Update Effect.Random to use any RandomGen as it's state
4. Assuming 2+3, can the effects library depend on contrib? If not, how to structure this?
5. Existing implementation of rndInt is not optimal, it uses the least significant bits, whereas Numerical Recipes in C states we should always use the most significant bits.

I have most of this coded already, and interestingly, I can avoid changing the existing Effect.Random interface at all by adding an implementation of RandomGen for Integer.

[farrellm]

I should add, I could put System.Random in a third party library, but I was hoping to make Effect.Random depend on it, which would exclude third party libraries.

[farrellm]

I suppose the other option is to put System.Random in the effects library. A bit odd, but maybe the simplest solution.

[farrellm]

6. Switch generated type from Integer to Int?

Seems like random number generation is one of the places we would prefer the performance of Int. Maybe the old RNG needed Integer for the calculation? But I think the return type should be Int.

[rbarreiro]

The effects library has been deprecated in favor of Control.ST, that is on contrib. You could check it on the tutorial. Em 13/11/2017 5:32 da manhã, "Matthew Farrell" <notifications@github.com> escreveu: 1. Switch generated type from Integer to Int? Seems like random number generation is one of the places we would prefer the performance of Int. Maybe the old RNG needed Integer for the calculation? But I think the return type should be Int. — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#4193 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AAM9NmIi6Q_KBw8HRiK8WcgfKJhGfwbOks5s19RdgaJpZM4QbKPY> .

[ahmadsalim]

@farrellm You are welcome to open a PR improving the random generation.
As @rbarreiro mentioned, it would be good if you added the changes to Control.ST in contrib.

[ahmadsalim]

@farrellm Additionally, please submit your contributions primarily to contrib, including System.Random.

[farrellm]

Makes sense, I'll move my changes from Effect to Control.ST

A note on the tutorial, I saw the notice, but read it as only Effect.ST being deprecated. Probably worth adding a note explicitly stating the entire effects library is deprecated.