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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