On Mon, Dec 15, 2008 at 09:04:34AM -0500, Jacques Carette wrote:
> AFAIK, extensions are not ordered, so trying to use camlp4 to deal
> with IFDEF in the source of a syntax extension (like pa_monad) to
> switch between 3.10 and 3.11 [to deal with the new private and lazy
> features] does not seem possible.

Why so?

When you build a camlp4 extension you're compiling some code relying
on camlp4 _as a library_. The code you're actually compiling is
compiled by the ocaml compiler, which can possibly receive it from
whatever pre-processor. That pre-processor can of course be camlp4
itself, loading some other camlp4 extension.

In short:

  ocamlc -pp "camlp4o available_ext.cmo" -c new_ext.ml

should work.

Of course, as observed, you can have grammar conflicts between the two
extensions, but that's an entirely different problem.

Cheers.

-- 
Stefano Zacchiroli -o- PhD in Computer Science \ PostDoc @ Univ. Paris 7
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