ketil@ii.uib.no (Ketil Z. Malde) writes: <snip OP>
Depending on why you need random numbers, you might want to consider using a fixed seed, i.e.
a = randoms (mkStdGen 4711)
will get you a sequence of "random" numbers. Of course, it will be the same sequence for every run of your program, but in some cases, (when you only want arbitrary data, and not necessarily random) this won't matter much.
The advantage is, of course, that you get rid of the IO monad. I've toyed with the idea of using unsafePerformIO (at least to get the seed), but haven't quite dared (or needed) to yet. :-)
well, thanks to all for the help. in my case, it was not OK to have arbitrary data, i needed (pseudo-) random numbers for different runs of the program. i want to: -generate random Ints -do some arbitrary computations on them to generate a [[Int]] -compare each [Int] in the list with a list of [Int] known at compile time the functions below seem to be doing what i need; i'm posting the code in case it helps other newbies get there a bit faster than i did. any constructive criticism / pointing out of errors most welcome. code:
import Random
rollDice :: IO Int rollDice = getStdRandom (randomR (1,6))
getRandomSeed :: IO Int getRandomSeed = do retval <- rollDice return retval
getRandomSeedInt :: IO Int -> Int getRandomSeedInt x = unsafePerformIO x
getARange :: Int -> Int -> [Int] getARange x y = randomRs (x,y) (mkStdGen (getRandomSeedInt getRandomSeed))
getRandomInt :: Int -> Int getRandomInt x = head (take 1 (getARange 0 x ))
output: Main> take 20 (getARange 0 10) [5,8,1,8,2,8,9,7,1,4,6,2,5,8,6,2,10,0,7,10] Main> take 20 (getARange 0 10) [9,8,9,9,7,2,4,5,1,7,2,2,8,2,5,10,5,3,1,8] thanks and regards, peter