On Fri, Nov 12, 2010 at 3:33 AM, Richard Senington <sc06...@leeds.ac.uk> wrote:
> 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''
>>>
>>>
>>>
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>>
>>
>
>
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