Re: Of foreach loops and counting

For testing "every third iteration," I do this sometimes:

my $n = 0;
foreach (@array) {
    next if I_dont_care_about($_);
    do_something_with ($_);
    print "." if !($n++ % 3);
}
print "\n";
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If you aren't necessarily processing every item in the list, but only want to count the number of elements you process, then using a temporary variable as you were doing is a useful alternative to looping over the array indices. It also works when you're doing things like looping over hash keys, where you can't count on having a numeric index implicitly; or processing lines of a file with a while (<>) loop.

Update: KM, that is definitely true, and a more efficient and succinct way to count lines when you're interested in the total line count. The method I presented is still useful when you want to count the number of lines you processed, not the total line count so far.

Alan

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RE: Re: Of foreach loops and counting by KM (Priest) on Aug 09, 2000 at 20:29 UTC
or processing lines of a file with a while (<>) loop. In that case, you can use $. (perldoc perlvar) to know what line you are in. For example: `#!/usr/bin/perl while (<DATA>) { print $. . ": $_"; } __DATA__ a b c d e f g h i # Would display when run... $ ./test.pl 1: a 2: b 3: c 4: d 5: e 6: f 7: g 8: h 9: i` [download] Cheers, KM	[reply] [d/l]