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Re: push parser implemenation

From: Paul Eggert
Subject: Re: push parser implemenation
Date: Tue, 12 Sep 2006 11:25:11 -0700
User-agent: Gnus/5.1008 (Gnus v5.10.8) Emacs/21.4 (gnu/linux)

Bob Rossi <address@hidden> writes:

> This would mean that the user would have to do "%push-parser
> %parse-param (void *PVVOID)" in order to get a valid push parser,
> instead of just doing %push-parser.  I think this would cause a lot
> of user confusion.
> Plus, the yyparse function internally uses the parameter PVVOID, in
> order to access the push parser.

Sorry, I don't know the details of the yyparse function, but I'll
try to explain my motivation here.

If there's an opaque type that the user must pass to yyparse no matter
what, then you're right, this should be built in: %parse-param should
be used only for extra parameters that the user wants to pass to the

However, all other things being equal I'd rather that the opaque type
were not void *.  In C, it's better to make it struct yysomething *,
where struct yysomething is an incomplete type.  That makes it more
likely that type errors will get caught at compile time, since struct
yysomething * is compatible only with itself, whereas void * is
compatible with lots of invalid pointer types.

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