i'll try a very non-technical explanation that has worked for me so far. (is it correct? does it make sense?) IO and ST are quite similar. the difference is that whereas IO gives you a concept of time in the world surrounding your code, ST lets you create a little bubble inside your code in which you can maintain state, while the bubble as a whole acts all pure and lazy. for example, if you want to implement an algorithm that writes to and reads from a matrix, you use ST: you want to control the order in which you read from and write to it, but not the order in which access events to that data structure mixes with user interaction events. -matthias On Mon, Oct 12, 2009 at 12:25:43AM -0700, Michael Mossey wrote:

To: Haskell Cafe Cc: From: Michael Mossey Date: Mon, 12 Oct 2009 00:25:43 -0700 Subject: [Haskell-cafe] statistics package and randomness

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?

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?

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?

Thanks, Mike

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