Re: Syntax diagram driven parser

"Joachim Durchholz" <joachim_d@gmx.de>
10 Oct 2000 00:53:48 -0400

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[11 earlier articles]
Re: Syntax diagram driven parser sebmol@gmx.net (Sebastian Moleski) (2000-10-01)
Re: Syntax diagram driven parser irobot@swbell.net (Brian Webb) (2000-10-01)
Re: Syntax diagram driven parser vbdis@aol.com (2000-10-01)
Re: Syntax diagram driven parser vbdis@aol.com (2000-10-08)
Re: Syntax diagram driven parser vbdis@aol.com (2000-10-08)
Re: Syntax diagram driven parser aaron1000@webtv.net (2000-10-08)
Re: Syntax diagram driven parser joachim_d@gmx.de (Joachim Durchholz) (2000-10-10)
Re: Syntax diagram driven parser vbdis@aol.com (2000-10-12)
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From: "Joachim Durchholz" <joachim_d@gmx.de>
Newsgroups: comp.compilers
Date: 10 Oct 2000 00:53:48 -0400
Organization: Compilers Central
References: 00-10-013 00-10-037
Keywords: parse, tools

VBDis <vbdis@aol.com> wrote:
>
> The resulting grammar uses my own extensions to BNF, with context
> variables.


Ah. This sounds similar van Wijngaarden Two-Level grammars. These are
context-sensitive, just like your grammar is. They can also be used
to express typing constraints, so you wrote something much more
powerful than you might have intended.


> In the OPL syntax also cases exist, where the kind of a symbol is
> important, whether it represents e.g. a constant value, a module name
> etc. I'm not very familiar with theory of grammars, but I doubt that
> a parser would be able to determine the kind of a symbol, which is
> imported from another module, and thus *cannot* know which syntax rule
> to use.


Hmmm... you'd have to parse the imported module as well to gain that
information. Or learn how to decipher the format of compiled Delphi
modules.
Yuck.


I don't know the actual Delphi syntax and what you're exactly trying to
do. It might be a good idea to write a grammar that's context free and
occasionally accepts a grammatically wrong Delphi program. (That's the
classical approach for add-on tools that are not compilers in
themselves.)


Regards,
Joachim


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