[Haskell-cafe] Random numbers / monads - beginner question

Claude Heiland-Allen claudiusmaximus at goto10.org
Thu May 8 06:47:59 EDT 2008

Madoc wrote:
> Given a list of numbers, I want to modify each of those numbers by adding a
> random offset. However, each such modified number shall stay within certain
> bounds, given by the integers minValue and maxValue. After that, I want to
> continue computation with the resulting list of type [Int].

Personally, I'd do something like this, isolate the IO code outside the 
algorithm to keep the algorithm pure:

modify' :: Int -> Int -> Int
modify' offset a =  normalize (a + offset)

generateInfiniteListOfRandomNumbers :: IO [Int]
-- implementation left as an exercise

main = do
   randomNumbers <- generateInfiniteListOfRandomNumbers
   print $ zipWith modify' randomNumbers [0, 200, 400, 600, 800, 1000]

hope this helps,


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