Don Stewart
joshua:
Is there any kind of intermediate form that a person can examine to see how their code is being optimized? Anything like EXPLAIN PLAN in SQL? It would make it much easier to understand the kinds of optimizations Haskell can perform.
I'm not looking so much for profiling -- obvious this program is trivial and takes no time. I just want to better understand what kind of optimizations are possible given Haskell's language model.
So the optimization you're looking for here is fusion of some kind. GHC ships with build/foldr fusion, and there are libraries for an alternative system, stream fusion.
GHC uses an intermediate representation called 'Core', which is a mini-Haskell, essentially, that is optimized repeatedly via type-preserving transformations. You can inspect this with a number of tools, including "ghc-core" (available on Hackage).
Excellent Don, thanks a lot for taking the time to spell this out for me. I don't understand it all yet, but I know what to dig into next time I want to observe the compiler's behavior. Josh