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Re: proposal: simplify prologue alternatives into %code

From: Hans Aberg
Subject: Re: proposal: simplify prologue alternatives into %code
Date: Tue, 9 Jan 2007 15:35:57 +0100

On 9 Jan 2007, at 15:10, Paolo Bonzini wrote:

The changes are small. But on should also keep the door for other langauge than C/C++/Java.

Keeping the door open, yes. But not at the cost of complicating needlessly what already exists now.

Keeping things well structured avoids that.

I'm also against a new directive such as your %cast, since Bison already has too many and -- in this particular case -- a simple % define is all that is needed.
Well, it is a fundamental feature of Bison that needs to be expanded. So one adds commands to help the user. If, in principle, all commands could be replaced by %define, woud you want to use it?


That is not a principle of ordinary computer language design, then.

I mean, "%union" or "%initial-action" could be replaced by "%code", and so could many other commands. Not "%left" and friends, for sure.

Well, %union can't be changed because of legacy (and compatibility with POSIX, I gather).

If you look back, I suggested %code should introduced for code placements instead of %define, to help up the users, and unifying different such code placements into one. And Bison development is now moving along that path.

The trick is to keep things structured. Those features that are related, should one attempt to unify. Others: keep separate.

  Hans Aberg

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