[Haskell-cafe] attoparsec double precision, quickCheck and aeson

Bryan O'Sullivan bos at serpentine.com
Tue Jun 5 19:51:08 CEST 2012


On Tue, Jun 5, 2012 at 9:12 AM, Warren Harris <warrensomebody at gmail.com>wrote:

>
> which helps in many cases, but for some the parsing seems bi-stable,
> alternating between two imprecise double values and causing the test to
> fail. I was wondering if anyone could suggest a better work-around for this
> problem, or explain why Attoparsec's double parser can't be isomorphic to
> haskell's.
>

If you need the full precision, use rational instead. The double parser is
there because parsing floating point numbers is often a bottleneck, and
double intentionally trades speed for precision.
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