[Haskell-cafe] is proof by testing possible?

[Dan Piponi]

Joe,

> On Mon, Oct 12, 2009 at 11:03 AM, Joe Fredette <jfredett at gmail.com> wrote:
> I completely forgot about free theorems! Do you have some links to resources
> -- I tried learning about them a while
> ago, but couldn't get a grasp on them... Thanks.

There is Wadler's paper but I do find it tricky:
http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.38.9875

You can play with the generator here:
http://linux.tcs.inf.tu-dresden.de/~voigt/ft/
The results can look unreadable at first, but I find that if I copy
them onto paper and do all of the remaining substitutions manually
(like I had to do with (a,b) -> (b,a)) you end up with something
readable. If you keep doing this you'll get a good intuition for what
the free theorem for a type will look like.
--
Dan