[Haskell-cafe] statistics package and randomness

Bryan O'Sullivan bos at serpentine.com
Mon Oct 12 14:01:00 EDT 2009

On Mon, Oct 12, 2009 at 12:25 AM, Michael Mossey <mpm at alumni.caltech.edu>wrote:

> I'm trying to learn how to use randomness in Haskell and it seems very
> non-straightforward and complex. I could do a lot of things using 'split'
> from System.Random, but apparently it's broken. There is the statistics
> package here:
> http://hackage.haskell.org/package/statistics
> Is this a better solution?

Yes, as it's much faster, more robust, and (depending on your perspective)
easier to use, provided you understand the ST monad.

> It uses the ST monad in the RandomVariate module. Can someone point me to a
> tutorial explaining ST, and/or a tutorial in the RandomVariate module?

For a tutorial on grokking ST, I'd suggest chapter 26 of Real World Haskell,
but I'm biased, since I wrote it:


Note that this already assumes that you understand monads pretty well.

Pseudorandomness seems like one case where it would just be a hell of a lot
> simpler to have a global generator--never split the state. Is the ST monad
> some way to accomplish this?

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