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Postings from September 2009
On Sunday 06 September 2009 10:40:44 Shlomi Fish wrote:
> Hi all!
>
> Which parser generator do you recommend to use for a Perl project. What
> I've looked at so far:
>
> 1. Berkeley Yacc for Perl - works pretty well, but is kinda limited.
Can't say i've used it before, but if its really Yacc then i believe that
Parse::Yapp does a better job of having a perl yacc.
> 2. Parse::RecDescent - very impressive feature set, but a little slow, and
> has been under-maintained (though it seemed to have improved slightly with
> several new releases in 2009). It also tends to be hard to debug its
> errors.
I've mostly had issues with either speed or getting precedence right with
Parse::RecDescent
> 3. Parse::Yapp - http://search.cpan.org/dist/Parse-Yapp/ - I tried to use
> it in https://svn.berlios.de/svnroot/repos/web-cpan/Text-Qantor/ but it
> gives me an error for what appears to be a valid syntax, and for the life
> of me I cannot understand why it is.
there's an ambiguity there in your grammar, i've run into that many times with
Math::Farnsworth
yapp -v will make a file.output that describes everything in the grammar and
can easily help with the debugging of things, the warnings about useless and
unused terminals are harmless (though could mean you've got a
typo). useless rules just means that they're in there but can't be reached,
its sort of like
if (something that is always true)
{
do something here
}
else
{
die "true != true";
}
your shift reduce conflict is in the rule
plain_para_text: TEXT
| plain_para_text TEXT { my $t1 = $_[1] ; my $t2 = $_[2] ; [$t1->[0].$t2-
>[0], $t1->[1]] }
;
its happening because it can recurse infinitely on itself and then see the TEXT
rule, (it'd also be expecting a second TEXT after that)
i'm not 100% sure what you were trying to do there, but the following rule
does what i THINK you were intending
plain_para_text: TEXT { my $t1 = $_[1] ; my $t2 = $_[2] ; [$t1->[0].$t2->[0],
$t1->[1]] };
as far as bison and ANTLR go i've never used either of them so i won't
comment, and i've got no idea about using PGE with perl so...
There's also Parse::Earley out there i played with that a bit but not as much
as i have with RecDescent and Yapp
P.S. sorry if this got sent twice, i found an oddity in my smtp settings and
don't think anything was ever making it out.
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