Re: Compiling expressions

Path	csiph.com!v102.xanadu-bbs.net!xanadu-bbs.net!news.glorb.com!news-out.readnews.com!news-xxxfer.readnews.com!news.misty.com!news.iecc.com!.POSTED!nerds-end
From	"Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Newsgroups	comp.compilers
Subject	Re: Compiling expressions
Date	Fri, 4 Jan 2013 10:18:26 +0100
Organization	cbb software GmbH
Lines	29
Sender	johnl@iecc.com
Approved	comp.compilers@iecc.com
Message-ID	<13-01-014@comp.compilers> (permalink)
References	<12-12-035@comp.compilers> <12-12-038@comp.compilers> <13-01-012@comp.compilers>
Reply-To	mailbox@dmitry-kazakov.de
NNTP-Posting-Host	news.iecc.com
Mime-Version	1.0
Content-Type	text/plain; charset="us-ascii"
Content-Transfer-Encoding	7bit
X-Trace	leila.iecc.com 1357317710 782 64.57.183.58 (4 Jan 2013 16:41:50 GMT)
X-Complaints-To	abuse@iecc.com
NNTP-Posting-Date	Fri, 4 Jan 2013 16:41:50 +0000 (UTC)
Keywords	parse
Posted-Date	04 Jan 2013 11:41:50 EST
X-submission-address	compilers@iecc.com
X-moderator-address	compilers-request@iecc.com
X-FAQ-and-archives	http://compilers.iecc.com
Xref	csiph.com comp.compilers:837

Show key headers only | View raw

On Thu, 3 Jan 2013 12:01:33 -0800 (PST), James Harris wrote:

>> I extended the method, which fairly old, towards non-associativity (#6),
>> advanced parenthesis (#5, keyed parameter associations), and split
>> association priorities into left-right pairs. But basically it is still the
>> same twin-stack method. Everything is table-driven, of course.
>
> Is it based on a Pratt parser? I see your comment and saw left and
> right priorities mentioned. I have never spent the time to understand
> Pratt parsers or why they need both. To deal with left- and right-
> associativity if I ever need to I was thinking to use the lowest bit
> of the precedence - something along the lines of clearing the bit on
> one side before a comparison. Then each operator would only need a
> single precedence.

Priority + direction sufficiently less general. For example it fails to
capture asymmetrically associated operations, e.g. assignment. Provided you
wanted assignment as an operator, you would like to have it rather this
way:

   a + b := c + d  --> a + (b := (c + d))

Priority + direction model cannot handle this. Here the left priority of :=
must be sufficiently higher than the right one.

--
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de

Thread

Compiling expressions James Harris <james.harris.1@gmail.com> - 2012-12-29 05:11 -0800
  Re: Compiling expressions glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2012-12-29 23:33 +0000
    Re: Compiling expressions James Harris <james.harris.1@gmail.com> - 2013-01-02 09:04 -0800
      Re: Compiling expressions "matzebraun@googlemail.com" <matzebraun@googlemail.com> - 2013-01-03 07:13 -0800
      Re: Compiling expressions Horst von Brand <vonbrand@inf.utfsm.cl> - 2013-01-14 16:31 -0300
  Re: Compiling expressions "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> - 2012-12-30 08:58 +0100
    Re: Compiling expressions James Harris <james.harris.1@gmail.com> - 2013-01-02 09:10 -0800
    Re: Compiling expressions James Harris <james.harris.1@gmail.com> - 2013-01-03 12:01 -0800
      Re: Compiling expressions "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> - 2013-01-04 10:18 +0100
  Re: Compiling expressions torbenm@diku.dk (Torben Ægidius Mogensen) - 2013-01-03 16:49 +0100
  Re: Compiling expressions James Harris <james.harris.1@gmail.com> - 2013-01-03 13:33 -0800
    Re: Compiling expressions James Harris <james.harris.1@gmail.com> - 2013-01-06 00:57 -0800
    Re: Compiling expressions "James Harris \(es\)" <james.harris.1@gmail.com> - 2013-03-07 11:11 +0000

csiph-web