Hi Stephen,
Are you rewriting Eijiro Sumii's MinCaml in Haskell?
Yes!
I did the same a couple of years ago, though I used Parsec for parsing and only implemented the higher transformations (beta reduction, inlining, constant folding, useless variable elimination). As I have no access to a Sparc machine, I didn't go as far as closure conversion and code generation.
At first I also used Parsec, but I wasn't happy with the parser. The original grammar has 4 left-recursive productions and I had to manually eliminate them(I guess you also did that). But after that the grammar was still not LL(1) so I had to place some `try`s very carefully. It worked fine, but resulting parser was parsing nested lets in exponential time. For example, this program took about a minute to parse: https://github.com/esumii/min-caml/blob/master/test/spill.ml . So I rewrote it in Happy and now it works great. (I still need to work on error messages though. Also, I did not resolve all ambiguities so Happy reports lots of shift-reduce conficts) I guess that problem with Parsec parser could also be fixed but I just prefer implementation to be similar to original definitions. (also, I always wanted to learn Happy since GHC is using it and I want to start contributing to GHC in the future) I love starting with some tutorials and then improving final product by adding more features etc. I started learning Haskell 3 years ago with "write yourself a Scheme" tutorial and then I added continuations/call-cc, exceptions and several other features. It helped me a lot and it was very fun way to learn. I'm currently planning to do something similar, I want to implement more features once I have compiler for the original language working. I also don't have a Sparc machine, so I'm planning to compile to x86-64. I only know basics of x86-64, so I want to first compile to C. After I have that working correctly, by looking to generated ASM from the generated C sources, I want to implement x86-64 code generator. So I also aim to learn x86-64 assembly. At some point I also want to implement a garbage collector.. AFAIK no heap allocation is done in the original language, so I may need some more data types.. Maybe sum-types or records like in Haskell.
The code was only for my personal learning as MinCaml was the nicest / smallest real compiler I could find. Code is in my Google repository - it might be useful for reference, obviously for a learning exercise you'd want to do-it-yourself:
https://code.google.com/p/copperbox/source/browse/ >> trunk >> compiler >> HMinCaml
Thanks! I may give it a look if I get stuck at some point. --- Ömer Sinan Ağacan http://osa1.net