random tune

[Ian Lynagh]

On Thu, Jul 09, 2009 at 11:42:20AM +0200, Laszlo Nagy wrote:
> 
> I also run the hlint program
> against the random library and applied the recommendations. Here are
> the patches:
> 
>   http://sites.google.com/site/rizsotto/patches/random-hlintclean.darcs

Thanks for taking the time to look into this.

I'd be interested in other people's opinions on whether the hlint
recommendations are an improvement or not.

In my opinion there are a handful of things that are slightly less clear
for no real benefit:

 createStdGen :: Integer -> StdGen
-createStdGen s = mkStdGen32 $ fromIntegral s
+createStdGen = mkStdGen32 . fromIntegral

   randoms  :: RandomGen g => g -> [a]
-  randoms  g      = (\(x,g') -> x : randoms g') (random g)
+  randoms  = (\(x,g') -> x : randoms g') . random

 theStdGen :: IORef StdGen
-theStdGen  = unsafePerformIO $ do
-   rng <- mkStdRNG 0
-   newIORef rng
+theStdGen  = unsafePerformIO $ mkStdRNG 0 >>= newIORef

In fact, I would change randoms to:

    randoms g = case random g of
                (x,g') -> x : randoms g'

And the rest aren't really better or worse in my opinion, e.g.:

 instance Random Int where
-  randomR (a,b) g = randomIvalInteger (toInteger a, toInteger b) g
-  random g        = randomR (minBound,maxBound) g
+  randomR (a,b) = randomIvalInteger (toInteger a, toInteger b)
+  random        = randomR (minBound,maxBound)

>   http://sites.google.com/site/rizsotto/patches/random-time.darcs

Thanks; I'll take a look at adding time to GHC's corelibs, and then
apply this.


Thanks
Ian