On Fri, Nov 12, 2010 at 3:33 AM, Richard Senington
In short, I am worried by the properties of this random number generator. I propose improving the testing system, and then posting both the test suite and this random generator to Hackage, unless you really want it up now in a very very preliminary form.
Yeah I think a package of randomness tests could be really useful. Cool :-)
RS
import System.Random
data LehmerTree = LehmerTree {nextInt :: Int, leftBranch :: LehmerTree, rightBranch :: LehmerTree}
instance Show LehmerTree where show g = "LehmerTree, current root = "++(show $ nextInt g)
mkLehmerTree :: Int->Int->Int->Int->Int->Int->LehmerTree mkLehmerTree aL aR cL cR m x0 = innerMkTree x0 where mkLeft x = (aL * x + cL) `mod` m mkRight x = (aR * x + cR) `mod` m innerMkTree x = let l = innerMkTree (mkLeft x) r = innerMkTree (mkRight x) in LehmerTree x l r
mkLehmerTreeFromRandom :: IO LehmerTree mkLehmerTreeFromRandom = do gen<-getStdGen let a:b:c:d:e:f:_ = randoms gen return $ mkLehmerTree a b c d e f
This can be pure:
mkLehmerTreeFromRandom :: (RandomGen g) => g -> LehmerTree
instance RandomGen LehmerTree where next g = (fromIntegral.nextInt $ g, leftBranch g) split g = (leftBranch g, rightBranch g) genRange _ = (0, 2147483562) -- duplicate of stdRange
test :: IO() test = do gen<-mkLehmerTreeFromRandom print gen let (g1,g2) = split gen let p = take 10 $ randoms gen :: [Int] let p' = take 10 $ randoms g1 :: [Int] -- let p'' = take 10 $ randoms g2 :: [Float] print p print p' -- print p''
_______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe