Re: Supporting multiple input syntaxes

From	"ltc...@gmail.com" <ltcmelo@gmail.com>
Newsgroups	comp.compilers
Subject	Re: Supporting multiple input syntaxes
Date	2021-03-14 21:08 -0400
Organization	Compilers Central
Message-ID	<21-03-001@comp.compilers> (permalink)
References	<20-08-002@comp.compilers> <21-02-004@comp.compilers> <21-02-005@comp.compilers> <21-02-008@comp.compilers>

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> Elijah Stone <elr...@elronnd.net> wrote:
> I did a C parser, it was not hard at all. I in C (like in standard
> Pascal) there are conflicts, but that conflicts can be resolved
> easily using semantic info. Alternativly, for C one can use 2
> token lookahead.

I'm not sure whether I captured the full context of your statement, but, if I
did, I don't think it's 100% correct:

- In regards to lookahead of 2:
This isn't enough to disambiguate, e.g., between a cast-expression in 6.5.4,
`( type-name ) cast-expression`, and a compound literal in 6.5.2, `( type-name
) { initializer-list }`.

- In regards to using semantic info:
Yes, with semantic info you can disambiguate things like `x * y;`, so I'd say
that, from a pragmatic/practical standpoint, this affirmation is right.
However, from a more theoretical perspective, a parser (thinking of it a
program that "simply" validates a sentence based on a grammar), isn't expected
— arguably — to rely on anything else other than syntax. Whether or not
the theoretical aspect of it is relevant, depends on the application of the
parser, I guess. For instance, for the implementation of static analysis tool,
not depending, as much as possible, on semantic information to guide parsing
is an advantage.

This is a table (only for expressions) that I recently put up when rewriting
the C parser of my project:
https://docs.google.com/spreadsheets/d/1oGjtFaqLzSoBEp2aGNgHrbEHxSi4Ijv57mXMP
ymZEcQ/edit?usp=sharing

--
Leandro T. C. Melo

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Thread

Supporting multiple input syntaxes luser droog <mijoryx@yahoo.com.dmarc.email> - 2020-08-12 15:20 -0700
  Re: Supporting multiple input syntaxes Kaz Kylheku <793-849-0957@kylheku.com> - 2020-08-13 00:43 +0000
  Re: Supporting multiple input syntaxes Hans-Peter Diettrich <DrDiettrich1@netscape.net> - 2020-08-13 10:27 +0200
    Re: Supporting multiple input syntaxes luser droog <mijoryx@yahoo.com.dmarc.email> - 2020-08-13 21:36 -0700
    Re: Supporting multiple input syntaxes luser droog <mijoryx@yahoo.com.dmarc.email> - 2020-08-23 22:16 -0700
  Re: Supporting multiple input syntaxes minforth@arcor.de - 2020-08-13 14:15 -0700
    Re: Supporting multiple input syntaxes luser droog <mijoryx@yahoo.com.dmarc.email> - 2020-08-13 21:37 -0700
    RE: Supporting mulitple input syntaxes Christopher F Clark <christopher.f.clark@compiler-resources.com> - 2020-08-14 12:44 +0300
  Supporting multiple input syntaxes David Lovemore <davidlovemore@gmail.com> - 2020-08-15 06:42 -0700
    Re: Supporting multiple input syntaxes luser droog <mijoryx@yahoo.com.dmarc.email> - 2020-08-15 15:20 -0700
      Re: Supporting multiple input syntaxes David Lovemore <davidlovemore@gmail.com> - 2020-08-16 02:21 -0700
        Re: Supporting multiple input syntaxes luser droog <mijoryx@yahoo.com.dmarc.email> - 2020-08-20 14:45 -0700
          Re: Supporting multiple input syntaxes luser droog <mijoryx@yahoo.com.dmarc.email> - 2020-08-23 19:35 -0700
            Re: implementation languages, was Supporting multiple input syntaxes luser droog <mijoryx@yahoo.com.dmarc.email> - 2020-08-23 20:39 -0700
              Re: implementation languages, was Supporting multiple input syntaxes Thomas Koenig <tkoenig@netcologne.de> - 2020-08-24 17:01 +0000
                Re: implementation languages, was Supporting multiple input syntaxes luser droog <mijoryx@yahoo.com.dmarc.email> - 2020-08-28 10:56 -0700
              Re: stack languages, was Supporting multiple input syntaxes luser droog <mijoryx@yahoo.com.dmarc.email> - 2020-08-24 12:14 -0700
  Re: Supporting multiple input syntaxes gah4 <gah4@u.washington.edu> - 2020-08-23 14:26 -0700
  Re: Supporting multiple input syntaxes antispam@math.uni.wroc.pl - 2021-02-11 23:27 +0000
    Re: Supporting multiple input syntaxes Elijah Stone <elronnd@elronnd.net> - 2021-02-17 01:44 -0800
      Re: Supporting multiple input syntaxes antispam@math.uni.wroc.pl - 2021-02-23 23:28 +0000
        Re: Supporting multiple input syntaxes "ltc...@gmail.com" <ltcmelo@gmail.com> - 2021-03-14 21:08 -0400
  Re: Supporting multiple input syntaxes Rock Brentwood <rockbrentwood@gmail.com> - 2021-03-14 17:36 -0700

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