Re: Is it the job of a parser to validate the input data?

Path	csiph.com!weretis.net!feeder6.news.weretis.net!news.misty.com!news.iecc.com!.POSTED.news.iecc.com!nerds-end
From	luser droog <luser.droog@gmail.com>
Newsgroups	comp.compilers
Subject	Re: Is it the job of a parser to validate the input data?
Date	Fri, 3 Sep 2021 21:37:53 -0700 (PDT)
Organization	Compilers Central
Lines	17
Sender	news@iecc.com
Approved	comp.compilers@iecc.com
Message-ID	<21-09-001@comp.compilers> (permalink)
References	<21-08-011@comp.compilers>
Mime-Version	1.0
Content-Type	text/plain; charset="UTF-8"
Injection-Info	gal.iecc.com; posting-host="news.iecc.com:2001:470:1f07:1126:0:676f:7373:6970"; logging-data="90378"; mail-complaints-to="abuse@iecc.com"
Keywords	parse, semantics
Posted-Date	04 Sep 2021 16:54:43 EDT
X-submission-address	compilers@iecc.com
X-moderator-address	compilers-request@iecc.com
X-FAQ-and-archives	http://compilers.iecc.com
In-Reply-To	<21-08-011@comp.compilers>
Xref	csiph.com comp.compilers:2698

Show key headers only | View raw

On Thursday, August 12, 2021 at 10:52:15 AM UTC-5, Christopher F Clark wrote:
> It is almost always done in the AST creation routines, not only do you
> as our insightful moderator mentioned generally get better error
> messages that way, but curiously, the features of extract a number,
> turn it into a count, and apply that count (and yes those might be 3
> distinct operations) to be how many items a list involves has not been
> implemented in any parser generator or lexer generator that I have
> ever seen. That's a bizarre omission, particularly since it is a
> common feature in many languages like networking protocols. Doing
> fixed counts isn't rare, but doing a count held in a "register" or
> "variable" seems to not be done.
>

I think the omission comes from difficulty in the formalization. Having to
apply such a dynamic count moves the parser from context-free to
context-sensitive, jumping to a new level in the Chomsky hierarchy.
So all the training wheels come off and it all gets scary.

Back to comp.compilers | Previous | Next — Previous in thread | Find similar

Thread

Is it the job of a parser to validate the input data? Christopher F Clark <christopher.f.clark@compiler-resources.com> - 2021-08-12 15:10 +0300
  Re: Is it the job of a parser to validate the input data? luser droog <luser.droog@gmail.com> - 2021-09-03 21:37 -0700

csiph-web