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POSystem.Random behaving very strangely; numbers displayed are not the numbers being operated on
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copied!<p>I needed to generate some random numbers for testing purposes. I have never used Data.Random before. I needed to do many tests and I would not know the amount of numbers I would need in advance, but I would know that they should fall into a certain bound. I wrote the function:</p> <pre><code>import System.Random f k = (\(x,y) -> x*y < (10^k) && x*y >0 ) rands n g k = take n $ filter (\(x,y) -> x*y < (10^k) && x*y >0 ) (zip a b) where a = randomRs (1::Int, 10^k-1) ga b = randomRs (1::Int, 10^k-1) gb (ga, gb) = split $ mkStdGen g </code></pre> <p>and began to test things using the numbers it generated. I began to notice strange things when using this function:</p> <pre><code>testRands n k = do g1 <- randomIO g2 <- randomIO let r = rands n (mkStdGen g1, mkStdGen g2) k putStrLn $ show r putStrLn $ show $ map (\(x,y) -> x*y < 10^k && x*y >0) r putStrLn $ show $ map (\(x,y) -> x*y) r putStrLn $ show $ maximum $ map (\(x,y) -> x*y) r *Main> testRands 4 7 [(6193574,9385226),(9634973,5475375),(5070277,7408626),(3801396,5652588)] [True,True,True,True] [4353660,6993107,2038586,4030960] 6993107 </code></pre> <p>I then copy the numbers it generated and paste them back into GHCI and call the exact same predicate function on all of them:</p> <pre><code>*Main> map (f 7) [(6193574,9385226),(9634973,5475375),(5070277,7408626),(3801396,5652588)] [False,False,False,False] </code></pre> <p>This makes no sense and I don't even know where to start trying to fix it.</p>

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