And no sooner do I send this email do I realize we have 'inline' built-in, so I can probably experiment with this right now... Edward Excerpts from Edward Z. Yang's message of Sun Aug 21 14:18:23 -0400 2011:
Hello all,
It occurred to me that it might not be too difficult to use GHC's optimization passes as a cheap and cheerful partial evaluator.
Consider some function we would like to partially evaluate:
f = g h
Partial evaluation proceeds as follows: calculate the type of f, inline and specialize g, inline and specialize h, and then optimize. Effectively, laser-guided inlining.
With this (very) heavy hammer, we can, for example, solve the problem posed in http://hackage.haskell.org/trac/ghc/ticket/1349, simply by ensuring all of our "strict functions" are partially evaluated on the continuation handler appropriately. (This is not ideal, since we ought to be able to share the strict worker/wrapper between instances, but might be a reasonable stop-gap for some use cases.)
So, am I completely insane, or does this seem plausible and easy enough to implement to make it into GHC?
Cheers, Edward