Re: [Haskell-cafe] Re: Generating repeatable arbitrary values with QuickCheck 2

Although now that I think about it, most of these could be pretty easily fixed by a new primitive:

splitGen :: Gen a -> Gen a splitGen m = MkGen spg where spg g n = (a, g2) where (g1, g2) = split g (a, _) = unGen m g1 n

Then you could do

infinite_xs <- splitGen $ sequence (repeat arbitrary)

-- ryan On Tue, Feb 2, 2010 at 2:04 PM, Ryan Ingram wrote:

On Tue, Feb 2, 2010 at 11:25 AM, David Menendez wrote:

...

We could avoid that problem by redefining Gen as a state transformer monad.

newtype Gen a = MkGen { unGen :: StdGen -> Int -> (a, StdGen) }

Unfortunately, this makes things like

...

 infinite_xs <- sequence (repeat arbitrary) no longer work, since the state never comes out the other side.

Which is a pretty significant change.

 -- ryan