On Jun 27, Steve Fink said:
>On Jun-26, Jeff 'japhy' Pinyan wrote:
>> I am currently completing work on an extensible regex-specific parsing
>> module, Regexp::Parser. It should appear on CPAN by early July (hopefully
>> under my *new* CPAN ID "JAPHY").
>>
>> Once it is completed, I will be starting work on writing a subclass that
>> matches Perl 6 regexes, Regexp::Perl6 (or Perl6::Regexp, or
>> Perl6::Regexp::Parser). I think this might be of some use to the Perl 6
>> dev crew, but I'm not sure how.
>
>Sounds interesting, but I'm a bit confused about what it is. Clearly,
>it parses regexes, but what is the output? A parse tree? Tables and/or
>code that implement a matching engine for that regex? PIR? A training
>regimen that can be used to condition a monkey to push a "yes" or "no"
>button whenever you give it a banana with an input string inscribed on
>it?
It creates a tree structure, not identical but similar to the array of
nodes Perl uses internally.
/a+?(bc|d|e)+/
is represented as
[
MINMOD(
PLUS(
EXACT('a')
)
),
PLUS(
ALT(
EXACT('bc'),
ALT(
EXACT('d'),
EXACT('e'),
)
)
)
]
Two signficant differences are that (?ismx-ismx) and (?ismx-ismx:...)
assertions are found explicitly in the parse tree. To Perl, in-place flag
changing doesn't need to stick around, because it has already had its
effect. Same deal with (?:...), really; it only serves to separate part
of the regex for a specific operation, and doesn't have a regex opcode.
For my module, though, it's helpful to keep these things around.
That might change before I release the module, though. I'm not sure yet.
For something like /a(?:b|c)d/, the tree can be
[
EXACT('a'),
ALT(EXACT('b'), EXACT('c')),
EXACT('d'),
]
See, no need for an explicit NOCAPTURE node or something. And if it was
/a(?i:b|c)d/, then I would do
[
EXACT('a'),
ALT(EXACTF('b'), EXACTF('c')),
EXACT('d'),
]
The trick is, when it comes time to create a physical regex from the tree,
I'd need to create (?flag) things on the fly. Which probably isn't too
hard.
Either way, there *will* be (?flag) and (?flag:...) objects created so
that the user knows of their existence during node-by-node parsing. They
just might not get included in the tree.
--
Jeff "japhy" Pinyan [EMAIL PROTECTED] http://www.pobox.com/~japhy/
RPI Acacia brother #734 http://www.perlmonks.org/ http://www.cpan.org/
CPAN ID: PINYAN [Need a programmer? If you like my work, let me know.]
<stu> what does y/// stand for? <tenderpuss> why, yansliterate of course.
