Looking for help writing some GHC RULES

Henning Thielemann schlepptop at henning-thielemann.de
Wed Jul 23 08:06:23 UTC 2014

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.


shows you the rules that fired and


shows the Core outputs, that the simplifier phase produce.

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