executing code within a regex

ColonelPanic has asked for the wisdom of the Perl Monks concerning the following question:

Hi everyone,

I am having problems with the (?{}) construct within a regex. In the code below, the print statement works fine. However, nothing gets pushed to the array. Does anyone have any insight on what is happening here? The input is on a line of C code. Thanks in advance.

Update: Oh yes, I'm using 5.8.3 ActiveState on Win32.


my @conds;
my $outer_conditional = qr/
   (
   #(??{$term})
   (?:
      (?: && | \|\| | & | \| | \^ )
      #(??{$term})
   )+
   )
   (?{push(@conds, $^N), print "   cond $^N\n"})
/x;

while ($line =~ /$outer_conditional/g)
{
   my $conds = join ", ",@conds;
   print "Conditionals: $conds\n";
}
[download]

--ColonelPanic

When's the last time you used duct tape on a duct? --Larry Wall

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Re: executing code within a regex by tilly (Archbishop) on May 07, 2004 at 21:33 UTC
For the record, if $line is set to "hello && world \|\| other" then the output that I get is: `cond && Conditionals: && cond \|\| Conditionals: &&, \|\|` [download] which I think is what you want. So I'd suggest filing a bug report. (This was tested in Perl 5.8.3 under Linux.)	[reply] [d/l]
Re: Re: executing code within a regex by ColonelPanic (Friar) on May 07, 2004 at 21:36 UTC
Thanks a lot for trying it out. I guess I'll have to work around that for now. When's the last time you used duct tape on a duct? --Larry Wall	[reply]
Re: executing code within a regex by BrowserUk (Patriarch) on May 07, 2004 at 22:18 UTC
Strange. Using AS809 (5.8.3 for win32), I get the expected results. `$line = 'this && that \|\| other & these \| those'; output: P:\test>test3 cond && Conditionals: && cond \|\| Conditionals: &&, \|\| cond & Conditionals: &&, \|\|, & cond \| Conditionals: &&, \|\|, &, \|` [download] Examine what is said, not who speaks. "Efficiency is intelligent laziness." -David Dunham "Think for yourself!" - Abigail	[reply] [d/l]
Re: executing code within a regex by hv (Prior) on May 07, 2004 at 23:00 UTC
It isn't entirely clear what you're seeing compared to what you expect to see, but I can't see a problem with the code you show under 5.8.3 on Linux. One thing that might be worth a try is to replace the declaration: `my @conds;` [download] with: `our @conds;` [download] - depending on precisely how you're using this in the real code, it may be that the regexp-eval is failing to see the right variable. Hugo	[reply] [d/l] [select]
Re: executing code within a regex by dave_the_m (Monsignor) on May 07, 2004 at 23:03 UTC
Note that there are many problems with using lexical variables within (?{...}) contructs with current Perl; in your real program (as opposed to the snippet above), is where @cond is declared and where it is accessed more involved, eg is part of the code actually contained within a function?	[reply]
Re: Re: executing code within a regex by ColonelPanic (Friar) on May 10, 2004 at 12:37 UTC
Yes, it turned out that when I ran the code as displayed above, it worked. The problem went away when I moved the @cond variable to a greater scope. Thanks everyone for your help. When's the last time you used duct tape on a duct? --Larry Wall	[reply]