[Caml-list] Camlp4: syntax extension in source file

[Alain Frisch <frisch@clipper.ens.fr>]

Hello,

This thread about macro definition with Camlp4 reminds me of an idea I had
some time ago. The idea is to use the Toplevel lib to introduce Caml
syntax extension directly inside source file. Something like that:


SYNTAX
  let x = ....

  EXTEND
    expr: [ .... ];
  END
END


The code between SYNTAX and END is parsed, compiled and executed by Camp4
during the preprocessing phase; it modifies the syntax used to parsed the
remaining of the rest of the file (including perhaps following SYNTAX ...
END statements). This allows a limited kind of reflexivity:  the source
file describes its own syntax. It also gives the possibility to perform
some computations at compile time (the "x" above).


I cannot remember why I didn't succeed to make it work (I think I had
some problems because of limitations in what the toplevel library
exports).

Daniel - and others - do you believe the above proposition makes sense ?


-- Alain

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