Re: A proposal for more powerful text processing to be built in to Perl: Flex and Pushdown Expressions.
On Fri, 11 May 2001 08:29:07 -0500, Tad McClellan wrote:
On Thu, May 10, 2001 at 04:26:56PM -0700, Daniel S. Wilkerson wrote:
Flex - Put all of flex right into Perl.
Don't we already have that in Perl 5?
Sortof.
What he is proposing, is again the age old proposal of putting the
notion of (simple) grammars into Perl's regex engine.
Part of what he proposes, namely the events, can/could be done with
embedded perl code into the regex, AKA the infamous (?{...})
construct. The advantage over doing this in plain perl, as you showed,
is that includes the possibility for backtracking, all without any help
from the outside.
The (??{...}) construct might likely be used to match nested
parentheses, for example. I'm not really sure, I'm not too familiar with
this crash-prone feature.
--
Bart.
Re: A proposal for more powerful text processing to be built in to Perl: Flex and Pushdown Expressions.
On Thu, May 10, 2001 at 04:26:56PM -0700, Daniel S. Wilkerson wrote:
Flex - Put all of flex right into Perl.
Having a lexer in Perl is useful, but does it have to be built into
the core? There already are several lexer modules for Perl 5
(Parse::Lex, Lex, Parse::RecDescent...) and while they may be
benefited by certain small, sharp additions to Perl, they do rather
well outside the core (and it means the Perl 6 developers don't have
to add Yet More to their plate).
Pushdown expressions - Slightly more powerful regular expressions.
This modifier would require that all parentheses-like literals: () []
{} pair-up in order for the trailing one to match.
That might be handy, its been getting easier to do this sort of thing
in a regex but its still a bit less-than-obvious. Non-obvious enough
to require its own module: Text::Balanced.
Can't comment on the particular syntax you've chosen, but the idea
sounds useful.
--
Michael G. Schwern [EMAIL PROTECTED]http://www.pobox.com/~schwern/
Perl6 Quality Assurance [EMAIL PROTECTED] Kwalitee Is Job One
GuRuThuG make a channel called #Perl, and infest it with joking and
fun it doesnt make alot of sense.
Re: A proposal for more powerful text processing to be built in to Perl: Flex and Pushdown Expressions.
I consider that the biggest weakness of the regex implementation currently is that it can't easily return nested data structures. Of course, regex readability could always use work too. Larry
