[Haskell] Re: type class instance selection & search

[Conal Elliott]

Thanks for these pointers, Ken.  And belated thanks to Oleg for his reply in
June.  Impressive tricks!

Perhaps I'm not the only person who'd prefer a more straightforward
formulation of backtracking search?  Cheers,

  - Conal

On 7/31/07, Chung-chieh Shan <ccshan at post.harvard.edu> wrote:
>
> Conal Elliott <conal at conal.net> wrote in article <
> ea8ae9fb0707311208j9f3fcf7m92bef8f54aea3dd8 at mail.gmail.com> in
> gmane.comp.lang.haskell.general:
> > I keep running into situations in which I want more powerful search in
> > selecting type class instances.
>
> I agree that it's quite useful for instance search to backtrack, if not
> desirable in all cases.  Proof search is program search, after all.
>
> Of course, allowing undecidable instances, we can build backtracking
> into instance search ourselves by representing the state of a
> backtracking machine as a type.  http://okmij.org/ftp/Haskell/poly2.txt
>
> --
> Edit this signature at http://www.digitas.harvard.edu/cgi-bin/ken/sig
> And if thou gaze into the abyss, the abyss...actually finds you pretty
> creepy.
>
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