Re: Random number generator

Thanks Stefan, Sorry for sending the message to the bug list. My first post to the users mailing list seems to get lost somewhere. I therefore try my luck on the bug list. It seems to work :) I am extending my polyGP system using the new haskell compiler. The random number is to be used for selecting crossover/mutation points, not to be printed (not IO type). I tried the following and they seem to work fine. -- get a list of random int between 1 and 250 drawInt :: [Int] drawInt = randomRs (1, 250)(mkStdGen 10) -- get a list of random double between 0 and 100 drawDouble :: [Double] drawDouble = randomRs (0, 100) (mkStdGen 100) Are they really random numbers ? I am wodering why all random double has values < 1.0. Do you know ? Thanks !! Tina Stefan Reich wrote: That's definitely not a message for the bugs list :-) Please have a look at this page: http://www.zvon.org/other/haskell/Outputrandom/getStdRandom_f.html It gives the correct signature for drawInt as you defined it: Int -> Int -> IO Int The signature you gave doesn't work because it specifies a pure function - for the same set of arguments, it must always produce the same result. How many ints do you want to generate? I don't think it is possible to generate an infinite lazy list in this case because this interferes with monad semantics. If you want a fixed number of random ints, try this: drawInts :: Int -> Int -> Int -> IO [Int] drawInts num x y = sequence (replicate num (getStdRandom (randomR (x,y)))) -Stefan Gwoing Yu wrote:

Hi,

I need some assistances in calling random number generator using 6.0.1 haskell compiler. To return a list of random int [Int], I have tried the following:

drawInt :: Int->Int -> [Int] drawInt x y = getStdRandom (randomRs (x,y))

It has a type error. I would appreciate if you know how to fix it.

Thank you in advance.

Tina Yu http://www.improvise.ws

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