Bugfix for QuickCheck 18.104.22.168
johan.tibell at gmail.com
Sun Aug 31 14:48:15 EDT 2008
On Sun, Aug 31, 2008 at 11:19 AM, Patrick Perry <patperry at stanford.edu> wrote:
> "variant" takes a generator and an integer, and produces a generator. Here
> is how it works in the new version:
> First, n gets written in binary:
> n = 10011
> Then, we replace "1" with "fst . split". and we replace "0" with "snd .
> n' = l . r . r . l . l where l = fst . split
> r = snd . split
> Then, we apply the resulting function to the generator
> g' = n' g0
> The run time is O (log n).
> In the old version, "split" gets called n times, so the run time is O(n).
> For certain double values, variant gets called with n on the order of 2^30,
> hence the hang in QuickCheck. The new version of variant employs the same
> algorithm as in QuickCheck2.
Thanks for the explanation!
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