Looking for help writing some GHC RULES

[Henning Thielemann]

Am 23.07.2014 00:42, schrieb David Feuer:
> I'm looking for some help writing some translate/untranslate rules to
> implement fusion for a couple of basic functions (the ones I'm looking
> at right now are takeWhile and scanr, but there may be others). I have a
> translation for takeWhile that seems to be at least decent, and one for
> scanr that is completely untested. I've never mucked about with GHC
> RULES, however, so I don't even know where to begin.

It is helpful to watch the simplifier working. E.g.

    -ddump-simpl-stats

shows you the rules that fired and

    -ddump-simpl

shows the Core outputs, that the simplifier phase produce.