Racc error recovery

4 Message(s) by 3 Author(s) originally posted in ruby programming

From: Aaron Patterson

Date: Wednesday, October 24, 2007

Hi everyone,

I'm writing a racc parser, and I need to recover from parse error

1. A discrepancy between a computed, observed, or measured
	value or condition and the true, specified, or theoretically
	correct value or condition.

	2. <programming> A mental mistake made by a programmer that
	may result in a program {fault}.

	3. (verb) What a program does when it stops as result of a
	programming error.

	(2000-03-28)

s.
Basically I'm writing a CSS

<World-Wide Web> (CSS) An extension to {HTML} to allow styles,
	e.g. colour, {font}, size to be specified for certain elements
	of a {hypertext} document.  Style information can be included
	in-line in the HTML file or in a separate CSS file (which can
	then be easily shared by multiple HTML files).  Multiple
	levels of CSS can be used to allow selective overriding of
	styles.

	{Home (http://www.w3.org/Style/CSS/)}.

	(2000-07-26)

parser, and I need to handle

1. <programming, operating system> A simple item of data that
	identifies a resource.  For example, a {Unix} file handle
	identifies an open file and associated data such as whether it
	was opened for read or write and the current read/write
	position.  On the {Macintosh}, a handle is a pointer to a
	pointer to some dynamically-allocated memory.  The extra level
	of indirection allows on-the-fly {memory compaction} or
	{garbage collection} without invalidating application program
	references to the allocated memory.

	2. <jargon> An alias used intended to conceal a user's true
	identity in an electronic message.  The term is common on
	Citizen's Band and other amateur radio but, in that context
	usually means the user's real name as {FCC} rules forbid
	concealing one's identity.

	Use of grandiose handles is characteristic of {crackers},
	{weenies}, {spods}, and other lower forms of network life;
	true hackers travel on their own reputations.

	Compare {nick}.

	[{Jargon File}]

	(2004-07-20)

poorly
formatted CSS.

Unfortunately I can not seem to find any good documentation

<programming> The multiple kilograms of macerated, pounded,
	steamed, bleached, and pressed trees that accompany most
	modern software or hardware products (see also {tree-killer}).
	Hackers seldom read paper documentation and (too) often resist
	writing it; they prefer theirs to be terse and {on-line}.  A
	common comment on this predilection is "You can't {grep} dead
	trees".

	See {drool-proof paper}, {verbiage}, {treeware}.

	[{Jargon File}]

	(2003-10-25)

or examples on
error recovery. I have read the Racc documentation about on_error and
entering "error recovering mode", as well as calling yyerrok to leave
error recovering mode, but I do not know what that actually means.

I have also discovered the "error" rule, but I do not want to explicitly
add that rule to every rule that could possibly have an error.

Any tips'd be greatly appreciated. Thanks!

--
Aaron Patterson
http://tenderlovemaking.com/

From: Giles Bowkett

Date: Thursday, October 25, 2007

I'm writing a racc parser, and I need to recover from parse errors.
..
Unfortunately I can not seem to find any good documentation or examples on
error recovery. I have read the Racc documentation about on_error and

Wild stab in the dark: is there any equivalent stuff in yacc

<tool, language> (yacc) The {LALR} {parser generator} found on
	most {Unix} systems.  Also, the language used to describe the
	{syntax} of another language to yacc (the program).

	Implementations: {ayacc}, {YAY}, {perln-byacc},

	SASL-Yacc - "Yacc in {SASL} - An Exercise in Functional
	Programming", Simon Peyton-Jones, Software Prac & Exp
	15:807-820 (1985).  Mentions also a BCPL implementation.

	Yacc++ - 1990.  An {object-oriented} rewrite of yacc, supports
	{regular expressions}, produces an {LR1 grammar} parser.

	["YACC Meets C++", S.C. Johnson, USENIX Spring '88 Conf].

	Chris Clark, Compiler Resources Inc, +1 (508) 435-5016.

	MLYACC - Implementation and output in {SML/NJ}.
	{(ftp:research.att.com/dist/ml/75.tools.tar.Z)}.

	A version, by David Poole at Montana University has been
	retargeted to {Turbo Pascal}.

	{(ftp://iecc.com/pub/file/lyprg.zip)}.

	See also {Bison}, {yet another}, {Yet Another Yacc}.

	{Unix manual page}: yacc(1).

	["YACC - Yet Another Compiler Compiler", S.C. Johnson, CS TR
	32, Bell Labs (Jul 1975)].

	[Was there ever an "ACC" - "Another Compiler Compiler"?  If
	so, what was the first compiler compiler called?]

	(2000-11-15)

you could
use as a starting point?

I realize it probably is not modeled that closely, but that's the first
thought I had.

Wild stab in the dark, part 2: tried using Sass instead? It's a CSS
DSL. Or do you've to work with the CSS you have already got?

--
Giles Bowkett

Blog: http://gilesbowkett.blogspot.com
Portfolio: http://www.gilesgoatboy.org
Tumblelog: http://giles.tumblr.com/

From: Aaron Patterson

Date: Friday, October 26, 2007

wrote in message:

> I'm writing a racc parser, and I need to recover from parse errors.
...
> Unfortunately I can not seem to find any good documentation or examples on
> error recovery. I have read the Racc documentation about on_error and
Wild stab in the dark: is there any equivalent stuff in yacc you could
use as a starting point?

Yes there is. I was hoping I could get an answer without digging up my
lex & yacc book. ;-) Fortunately I found it and there is an error
recovery section that has definitely helped.

I realize it probably is not modeled that closely, but that's the first
thought I had.
Wild stab in the dark, part 2: tried using Sass instead? It's a CSS
DSL. Or do you've to work with the CSS you have already got?

No. I'm trying to parse CSS, not generate

To produce something according to an {algorithm} or program or
	set of rules, or as a (possibly unintended) {side effect} of
	the execution of an algorithm or program.

	The opposite of {parse}.

	[{Jargon File}]

	(1995-06-15)

it.

--
Aaron Patterson
http://tenderlovemaking.com/

From: barjunk

Date: Sunday, October 28, 2007

On Oct 25, 10:29 pm, Aaron Patterson <aa...@xxxxxxxxxxx>
wrote in message:
wrote in message:
> > I'm writing a racc parser, and I need to recover from parse errors.
> ...
> > Unfortunately I can not seem to find any good documentation or examples on
> > error recovery. I have read the Racc documentation about on_error and
> Wild stab in the dark: is there any equivalent stuff in yacc you could
> use as a starting point?
Yes there is. I was hoping I could get an answer without digging up my
lex & yacc book. ;-) Fortunately I found it and there is an error
recovery section that has definitely helped.
> I realize it probably is not modeled that closely, but that's the first
> thought I had.
> Wild stab in the dark, part 2: tried using Sass instead? It's a CSS
> DSL. Or do you've to work with the CSS you have already got?
No. I'm trying to parse CSS, not generate it.
--
Aaron Pattersonhttp://tenderlovemaking.com/

Aaron,

Would you mind sharing some of what you found in the book? I'm more
interested in what you were thinking originally and then what the book
had to say to change your mind.

I'm interested in putting together some more documentation for Racc.

Mike B.

Next Message: .each do |foo, bar| what does bar do?

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