[moved to haskell-cafe] On Tue, 2005-06-28 at 14:46 -0700, John Meacham wrote:

Unfortunatly hat suffers from the same problem that pretty much every non-trivial preprocessor does, as soon as you start using ghc's special or experimental features that have not been added to hat yet, they stop working.

I agree this is a problem. [snip]

I am not sure what the general solution would be. perhaps hat being integrated with ghc?

I think it is preferable to keep them separate. Already a big effort was put into making hat independent of nhc98. There will always be more tools that Haskell could use, which must transform the source code one way or another. I'd rather not see them all be pushed inside ghc, or whatever other compiler was popular at the time. It's probably better for ghc's maintainability to keep these tools out of its source tree (pure speculation on my part though).

or better yet would be a standard interface for ghc to call a preprocessor but at some intermediate level where most of the extensions have been sugared away but most of the original source structure still exists... the nice thing about a standard interface would be that jhc and other compilers could support it too. It wouldn't even need to be a plugin based thing, but rather an executable that ghc can run and pass commands to it on stdin and read results on stdout.

Sounds nicer. Perhaps GHC-as-a-library might be close to what is needed. There is a danger that we won't be able to settle upon what is the right core language to use, and some tools will be left out, thus reverting to the solution employed by hat at the moment.

Being able to just work on any unmodified program the compiler supports is a huge feature.

Yes. The problem is that Haskell is being torn in two directions. One direction is a research vehicle. The other direction is a work-horse. GHC sits somewhere in the middle, and does an amazing job too. The trouble is that it has become a fast moving target. Overall I think Hat's solution is a reasonable compromise between the competing needs of the tool. If anything I would like to see the Haskell community produce a Haskell front end which was compiler neutral. That would facilitate many interesting projects, and that might even help with the need to support new extensions as they come along. There are already some candidates floating around, but it seems they are not widely adopted. Cheers, Bernie.