We have all the machinery available. See:
http://www.cs.uu.nl/groups/ST/Center/SyntaxMacros
It will be part of the UtrechtHaskellCompiler (UHC), that is being constructed with our toolset, and which recently strated to produce running code. You get the syntax macros "almost" for free if you build your parser with the UtrechtParserCombinators (UPC). You can experiment with it yourself for your own language.
The probem we are still working on is to handle left-recursive extensions being made by the user. We are well on our way with that. In principle we also know how to provide feedback to the user in terms of the extended input language, but unfortuantely the implementation is rather cumbersome.
Doaitse
On 2004 mei 15, at 17:49, Per Larsson wrote:
I have recently made a small detour into ocaml programming and I'm rather
impressed with the generic preprocessor 'camlp4' for ocaml. Camlp4 allows the
programmer to (i) interact with the ocaml parser and lexer to extend the
concrete grammar with new syntax and (ii) to directly define the translation
of such new syntax forms in terms of ocaml abstract syntax. Haskell
programmers (at least in GHC) can also manipulate abstract syntax with the
Template Haskell extension and the Language.Haskell.THSyntax library, but to
my knowing there is no haskell compiler which supports the inclusion of new
syntax forms. Wouldn't such a tool be cool? In the haskell community there
are a number of handmade preprocesserors (DrIFT, Generic Haskell, HaRP, ...)
which are both cumbersome to write, because the authors must write a
(partial) haskell parser for every small extension, but also cumbersome to
use because of increasing complexity to your makefiles and different
standards for error reporting. Also, experimental extensions could quickly be
written and evaluated by the haskell users, decreasing the dependency on the
compiler maintainers.
Per Larsson
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