"Steve Grazzini" <[EMAIL PROTECTED]> wrote in message news:[EMAIL PROTECTED]
> On Wed, Jul 16, 2003 at 06:50:21PM +0200, Kevin Pfeiffer wrote:
> > I found this in my "to do" directory (was this from perl.beginners - I don't
> > remember and can't find it via Google). I tried the "line-range" operator
> > here, but am wondering if it's possible with it to *not* catch the matching
> > lines (i.e. only lines "3"-"4"). I suppose if you captured into an array
> > then you could just shift and unshift. I also tried a second way below not
> > using range that seems to work well (or?).
>
> There's nothing wrong with the trick you used (and it might be
> easier to understand than mine) but you can also switch on the
> range operator's return value:
>
> while (<DATA>) {
> my $range = /line2/../line5/;
> print if $range > 1 # skip the first line
> and $range !~ /E/; # and the last (which looks like "4E0")
> }
>
> I don't think this is documented (is it?) but it can be handy.
No, I don't think it is documented (at least not on 5.6) but it's clear
you're meant to use it this way; this is one of the dark secrets of Perl.
I believe that
perldoc perlop (search for 'Range Operators')
should read something like
Each ".." operator maintains its own boolean state. It [returns a
sequence number starting at one] until the right operand is true,
*AFTER* which the range operator becomes false again.
With the adjunct that the last /true/ value of the operator will be expressed
in engineering format, witness the program below whichshows that the first
line and the last line can be tested by checking for a value of one and a
regex match of /E/ respectively.
Together with the difference between the .. and the ... operator, I shall
pause before I dig further...
HTH somebody :)
Rob
while (<DATA>) {
my $xx = /line2/ .. /line5/;
print defined $xx ? "'$xx'" : 'undef', "\n";
}
__DATA__
This is line1
some text on line2
line3 all about me
good stuff on line4
line5 isn't that great
I'm on line6
OUTPUT
''
''
'1'
'2'
'3'
'4E0'
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