newbie:: getting random Ints

Andre W B Furtado awfurtado@uol.com.br
Fri, 29 Mar 2002 16:19:21 -0300


the function
randomRIO :: (a,a) -> IO a
defined in module Random gives you a random number between the two input
parameters (including themselves).

-- Andre

----- Original Message -----
From: Peter Rooney <pt@panix.com>
To: <haskell-cafe@haskell.org>
Sent: Thursday, March 28, 2002 3:05 AM
Subject: newbie:: getting random Ints


>
> hello all,
>
> total newbie to haskell, armed with "the craft of functional
> programming".
>
> i can't seem to generate random numbers. i have read this:
>
> http://www.haskell.org/onlinelibrary/random.html
>
> and searched the web and archives, and read thru Random.hs (mostly
> over my head), but have been unable to get any combination of
> getStdRandom randomR, etc. to work. even the example in the 98 report,
>
> import Random
>
> rollDice :: IO Int
> rollDice = getStdRandom (randomR (1,6))
>
> gets me:
>
>
> Main> rollDice
>
> Main>
>
> after loading the file, which makes me think i'm missing something!
> TCFP has an example of how to do it yourself, but i can see that my
> needs are more than met by Random.hs.
>
> my various attempts all look a lot like this:
>
> Main> getStdGen (random 5)
> ERROR - Type error in application
> *** Expression     : getStdGen (random 5)
> *** Term           : getStdGen
> *** Type           : IO StdGen
> *** Does not match : a -> b
>
> could someone post an example of how to generate random integers
> within a range?
>
> tia,
> peter
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