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Re: trying out the c++ parser skeleton / b4_post_prologue

From: Hans Aberg
Subject: Re: trying out the c++ parser skeleton / b4_post_prologue
Date: Tue, 11 Jul 2006 23:31:45 +0200

On 11 Jul 2006, at 17:29, Joel E. Denny wrote:

On Mon, 10 Jul 2006, Anthony Heading wrote:

The right point appears to be the b4_post_prologue macro,
but bizarrely this seems to be inaccessible unless the
parser uses %union.

Thanks for the feedback. We've been debating how to clean this behavior


  A solution is actually implemented in CVS, but I'm not sure if that
one will stick.  You should see some sort of solution in Bison 2.4.

As proof-of-principle, I created a new directive (naturally
called "%no-union"!) which only flipped the prologue.  That
seemed to work OK, but I wonder if there's a better solution?

The developers are currently settling for very simple C++, and there is little chance you will be able to do normal C++ code writing via Bison 2.4 or whatever.

There is an experimental %define directive which can be used to place C++ code correctly, some time in the future when it can be used to place code, except for 1-liners. So you (Anthony Heading) are on right track: one needs a way to place code more accurately in order to do C++. In fact, I have made my own tweaks of Bison for last couple of years in order to place the C++ code correctly. :-) But I got tired of patching up the many frequent Bison releases, so I am currently stuck with Bison 2.0.

And when you use %union, the underlying C++ implementation must currently be untyped, not something that one would use in ordinary C+ + programming.

  Hans Aberg

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