Duncan Coutts wrote:
So you end up with pure functions like:
shuffle :: RandomGen g => g -> [x] -> [x]
Thanks for the help, Duncan. I'm confused on one point. Don't you always need
the new state of the generator back? So wouldn't this need to be:
shuffle :: RandomGen g => g -> [x] -> (g,[x])
Another approach is to hide the 'g' inside a monad. That's what
MonadRandom is all about. eg:
shuffle :: [x] -> Rand [x]
One tutorial mentions the class Gen in the Test.QuickCheck module. Is "Rand" a
different class defined somewhere else?
The tutorials above explain about the other random functions, for
getting values of different types (not just Int) and restricted ranges
of number etc.
Of course at some point you want to seed the random number generator
with some initial genuinely random value (not like the 12345 we used
above). That is the only place in your random-handling code that needs
to do IO. All the rest of it can be pure.
What function gives you that initial random seed? (Grabs it from the system
clock?)
Thanks,
Mike
_______________________________________________
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
