[Haskell] Re: type class instance selection & search

Conal Elliott <conal@conal.net> wrote in article <ea8ae9fb0707311208j9f3fcf7m92bef8f54aea3dd8@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.