---------- Forwarded message ----------
Date: Fri, 19 Apr 2002 19:06:30 -0400 (EDT)
From: Jeff 'japhy' Pinyan <[EMAIL PROTECTED]>
Reply-To: [EMAIL PROTECTED]
To: drieux <[EMAIL PROTECTED]>
Subject: Re: B/C - Re: help parsing file
On Apr 19, drieux said:
>> while (<FH>) {
>> next unless /^$prefix/;
>> $_ .= <FH> while /^$prefix/gm;
>> print;
>> }
>
>why is it that when I try to do this - my perldebugger
>goes out to lunch...
Because I messed up. I never actually ran that code -- it was what I
thought of doing, and it mutated to the final working code. Sorry.
The //g trick only works when the variable isn't changed. However, I'm
appending to $_, so the trick breaks. The trick can be unbroken in the
following manner:
while (<FH>) {
next unless /^$prefix/;
pos = (pos, $_ .= <FH>)[0] while /^$prefix/gm;
print;
}
pos() happens to hold the place where the next //g match starts from in
the string it matches against. It can be read from or written to.
$p = pos $str;
pos $str = 5; # that's pos($str) = 5, not pos($str = 5)
pos()'s default argument is $_. So we restore pos() to the value it had
prior to changing $_, and change $_ all at once. Trickery.
This cruft is another reason to use the flip-flop approach.
--
Jeff "japhy" Pinyan [EMAIL PROTECTED] http://www.pobox.com/~japhy/
RPI Acacia brother #734 http://www.perlmonks.org/ http://www.cpan.org/
** Look for "Regular Expressions in Perl" published by Manning, in 2002 **
<stu> what does y/// stand for? <tenderpuss> why, yansliterate of course.
[ I'm looking for programming work. If you like my work, let me know. ]
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