John W. Krahn wrote:
Mariano Loza Coll wrote:
Hi John,
Hello,
I'm trying to learn a little bit more of Perl everyday, and I was
intrigued about your earlier suggestion in a thread.
my $bad_chromosomes = qr/^(?:6|8|14|16|18|Y)\t/;
while (<$IN> ) {
print $OUT $_ if !/$bad_chromosomes/;
}
I get the spirit of what you suggested, but I was curious about the use
of "?:"
() are capturing parentheses and
(?:) are non-capturing parentheses.
If I got it right, the "?" will make the search non-greedy. But what
is the ":" for?
The (?:... ) notation is non-capturing. The ?: makes it non capturing.
In this context, the '?' is not used to control greediness.
In perlre, look for the section 'Extended Patterns', then down a page look
for:
(?:pattern)
(?adluimsx-imsx:pattern)
(?^aluimsx:pattern)
Chris
perldoc perlre
John
--
Any intelligent fool can make things bigger and
more complex... It takes a touch of genius -
and a lot of courage to move in the opposite
direction. -- Albert Einstein
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