Repository : ssh://darcs.haskell.org//srv/darcs/packages/random On branch : master
http://hackage.haskell.org/trac/ghc/changeset/69bfde219bab869729fdbe9c1496371f912bf41e >--------------------------------------------------------------- commit 69bfde219bab869729fdbe9c1496371f912bf41e Author: Ryan Newton <[email protected]> Date: Tue Dec 6 15:07:53 2011 -0500 Minor: comments only >--------------------------------------------------------------- System/Random.hs | 13 ++++++++++++- 1 files changed, 12 insertions(+), 1 deletions(-) diff --git a/System/Random.hs b/System/Random.hs index 5c91737..9a970c4 100644 --- a/System/Random.hs +++ b/System/Random.hs @@ -114,7 +114,11 @@ getTime = do -- | The class 'RandomGen' provides a common interface to random number -- generators. -- +#ifdef ENABLE_SPLITTABLEGEN -- Minimal complete definition: 'next'. +#else +-- Minimal complete definition: 'next' and 'split'. +#endif class RandomGen g where @@ -147,7 +151,7 @@ class RandomGen g where #ifdef ENABLE_SPLITTABLEGEN -- | The class 'SplittableGen' proivides a way to specify a random number --- generator that can be split into two new generators. +-- generator that can be split into two new generators. class SplittableGen g where #endif -- |The 'split' operation allows one to obtain two distinct random number @@ -423,14 +427,17 @@ randomIvalInteger (l,h) rng | otherwise = case (f n 1 rng) of (v, rng') -> (fromInteger (l + v `mod` k), rng') where k = h - l + 1 + -- ERROR: b here (2^31-87) represents a baked-in assumption about genRange: b = 2147483561 n = iLogBase b k + -- Here we loop until we've generated enough randomness to cover the range: f 0 acc g = (acc, g) f n' acc g = let (x,g') = next g in + -- We shift over the random bits generated thusfar (* b) and add in the new ones. f (n' - 1) (fromIntegral x + acc * b) g' -- The continuous functions on the other hand take an [inclusive,exclusive) range. @@ -454,6 +461,10 @@ randomIvalDouble (l,h) fromDouble rng int32Count :: Integer int32Count = toInteger (maxBound::Int32) - toInteger (minBound::Int32) + 1 +-- Perform an expensive logarithm on arbitrary-size integers by repeated division. +-- +-- (NOTE: This actually returns ceiling(log(i) base b) except with an +-- incorrect result at iLogBase b b = 2.) iLogBase :: Integer -> Integer -> Integer iLogBase b i = if i < b then 1 else 1 + iLogBase b (i `div` b) _______________________________________________ Cvs-libraries mailing list [email protected] http://www.haskell.org/mailman/listinfo/cvs-libraries
