On Mon, Jan 4, 2010 at 6:31 PM, Dale Jordan
Can anyone explain why this is looping or point out a better way to generate an arbitrary-length random list while still being able to reuse the generator? (I'd rather not use split since this generator doesn't support it and its of dubious soundness.)
Well there is more than one way to split. You don't have to split the generator -- if you act on a stream of random numbers, you can split the stream also: split :: [a] -> ([a],[a]) split (x:xs) = (x:bs,as) where (as,bs) = split xs However too much splitting in this case causes a performance penalty, since you start discarding large portions of the stream. If you don't want to split the generator, this is the only way I can think of that is deterministic in the random seed. If determinism is not required, as many times it is not with *random* computations, you can use the value-supply package on hackage, which uses a bit of unsafePerformIO magic to turn a serial stream into a splittable stream. But you lose composable repeatability. Luke