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Re: Calculating variable {n} in regex match

by temporal (Pilgrim)
on Jun 05, 2012 at 17:08 UTC ( #974507=note: print w/ replies, xml ) Need Help??


in reply to Calculating variable {n} in regex match

It sounds like the OP wants to capture the number of occurrences entirely within the regex, something like:

$foo =~ m/[0-9]({\d+})/ print "$foo has $1 digit(s)";

... if that were possible (it isn't). This would allow the counting match to be thrown in with a longer regex that is matching on other properties as well. This is probably possible through clever use of code evaluation (?{code}) and interpolation within the regex.

However, if all you need to do is count in the regex then you could use the 'goatse' operator:

my $length =()= $foo =~ /[0-9]/g; print "$foo has $length digit(s)";

Seems better than looping and incrementing, anyway.

Strange things are afoot at the Circle-K.


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Re^2: Calculating variable {n} in regex match
by atreyu (Sexton) on Jun 05, 2012 at 18:03 UTC
    ... if that were possible (it isn't). This would allow the counting match to be thrown in with a longer regex that is matching on other properties as well. This is probably possible through clever use of code evaluation (?{code}) and interpolation within the regex.

    that's actually kind of hoping for...a clever use of eval - but i couldn't figure that out. anyway, sounds like what i want is not possible, at least in a straight-forward fashion.

Re^2: Calculating variable {n} in regex match
by AnomalousMonk (Abbot) on Jun 05, 2012 at 19:49 UTC

    FWIW:

    >perl -wMstrict -le "my $s = '123 234 3456789 3210 34567'; ;; my @m = $s =~ m{ \b ((\d) (??{ qr{\d{$^N}} })) \b }xmsg; print qq{@m}; ;; my $i = 2; @m = $s =~ m{ \b (??{ ++$i; qr{\d{$i}}; }) \b }xmsg; print qq{@m}; " 234 2 3210 3 123 3456789
      okay, AnomalousMonk, this works:
      # the original number of integers to test (will be one-upped) my $i = 1; # the input string to be tested (a number) my $foo = shift; # see if the input string is a two-digit number my $rc = ($foo =~ m{ \b (??{ ++$i; qr{\d{$i}}; }) \b }xmsg) ?'Y' :'N';
      very clever...thanks.

        But sometimes cleverness can be a curse, so you may want to reserve your thanks until later.

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