Re^6: why my reg ex matches greedy?

It's different if there is some following match condition:

use strict;
use warnings;

for my $reg ('(x\d{3,}?)', '(x\d{3,}?x)', '(x\d{3,})', '(x\d{3})') {
    for my $str ('xx', 'x12x', 'x123456x', 'x12x x123x') {
        print "Matched using $reg: $1\n" if $str =~ $reg;
    }
}
[download]

Prints:

Matched using (x\d{3,}?): x123
Matched using (x\d{3,}?): x123
Matched using (x\d{3,}?x): x123456x
Matched using (x\d{3,}?x): x123x
Matched using (x\d{3,}): x123456
Matched using (x\d{3,}): x123
Matched using (x\d{3}): x123
Matched using (x\d{3}): x123
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True laziness is hard work

Comment on Re^6: why my reg ex matches greedy? Select or Download Code

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Re^7: why my reg ex matches greedy? by roboticus (Chancellor) on Jun 26, 2012 at 22:27 UTC
GrandFather: Thanks. I updated your code to make it a little more visually obvious to me, then added a couple cases. Now that I see what the difference is, I doubt that I'd ever use it. Not because it isn't useful, but rather because if I ever need it, I'm sure I'll have long forgotten it. But it's certainly educational. For grins, here's what I came up with: $ cat splok.pl use strict; use warnings; my @regs = ('(x\d{3,}?)', '(x\d{3,}?x)', '(x\d{3,})', '(x\d{3})', '(x\d{3,}x)', '(x\d{3,}?x?)'); my @strs = ('xx', 'x12x', 'x123456x', 'x12x x123x', 'x123456y'); printf "%-12.12s ", $_ for " ", @regs; print "\n"; for my $str (@strs) { printf "%-12.12s ", $str; for my $reg (@regs) { printf "%-12.12s ", ($str=~$reg) ? $1: '-nope-'; } print "\n"; } $ perl splok.pl (x\d{3,}?) (x\d{3,}?x) (x\d{3,}) (x\d{3}) (x\d{ +3,}x) (x\d{3,}?x?) xx -nope- -nope- -nope- -nope- -nope +- -nope- x12x -nope- -nope- -nope- -nope- -nope +- -nope- x123456x x123 x123456x x123456 x123 x1234 +56x x123 x12x x123x x123 x123x x123 x123 x123x + x123x x123456y x123 -nope- x123456 x123 -nope +- x123 [download] (As you can tell, I like things laid out in grids. I organize lots of stuff with database tables and spreadsheets...) ...roboticus When your only tool is a hammer, all problems look like your thumb.	[reply] [d/l]

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Re^7: why my reg ex matches greedy?
by roboticus (Chancellor) on Jun 26, 2012 at 22:27 UTC

GrandFather:

Thanks. I updated your code to make it a little more visually obvious to me, then added a couple cases. Now that I see what the difference is, I doubt that I'd ever use it. Not because it isn't useful, but rather because if I ever need it, I'm sure I'll have long forgotten it. But it's certainly educational.

For grins, here's what I came up with:

$ cat splok.pl
use strict;
use warnings;

my @regs = ('(x\d{3,}?)', '(x\d{3,}?x)', '(x\d{3,})',
             '(x\d{3})',   '(x\d{3,}x)',  '(x\d{3,}?x?)');
my @strs = ('xx', 'x12x', 'x123456x', 'x12x x123x', 'x123456y');

printf "%-12.12s ", $_ for " ", @regs;
print "\n";
for my $str (@strs) {
    printf "%-12.12s ", $str;
    for my $reg (@regs) {
        printf "%-12.12s ", ($str=~$reg) ? $1: '-nope-';
    }
    print "\n";
}

$ perl splok.pl
             (x\d{3,}?)   (x\d{3,}?x)  (x\d{3,})    (x\d{3})     (x\d{
+3,}x)   (x\d{3,}?x?)
xx           -nope-       -nope-       -nope-       -nope-       -nope
+-       -nope-
x12x         -nope-       -nope-       -nope-       -nope-       -nope
+-       -nope-
x123456x     x123         x123456x     x123456      x123         x1234
+56x     x123
x12x x123x   x123         x123x        x123         x123         x123x
+        x123x
x123456y     x123         -nope-       x123456      x123         -nope
+-       x123
[download]

(As you can tell, I like things laid out in grids. I organize lots of stuff with database tables and spreadsheets...)

...roboticus

When your only tool is a hammer, all problems look like your thumb.

[reply]
[d/l]