ciamack has asked for the wisdom of the Perl Monks concerning the following question:

Hi all
I extract texts between HTML tags to an array and some of
them are pure integer numbers. I need to examin each
item within this array and use those numbers.

if ($item =~ ?????????){
#do something with the number
}

I appreciate any suggestion
Thanks
  • Comment on How to determine a variable value is a number

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Re: How to determine a variable value is a number
by elusion (Curate) on Aug 03, 2002 at 01:03 UTC
    In a regex, \d stands for a digit, so if you use
    if ($item =~ /^\d+$/) {
    # do something
}

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    It will do something for every item that contains only digits. The ^ marks the start and $ marks the end of the string, telling the regex that you want it to match only if every character can be matched. Hope this helps.

    elusion : http://matt.diephouse.com

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Re: How to determine a variable value is a number
by larsen (Parson) on Aug 03, 2002 at 13:07 UTC
[reply]
      Interesting. Let me know if I've got this strait: 
      #!/usr/bin/perl -w

use strict;

sub i_am_a_number {
    shift;
    no warnings; # += 0 on a string sets off a warning

    # make sure that zero is counted as a number
    # ($_ += 0) alone fails on zero.
    if (/^\d+$/ || ($_ += 0)) {
        return 1;
    }
    return 0;
}

#############################################################
# take the sub on a test spin
my @list = (035, 35, +19, 12, "045", -2, 5.5, 0, -34.530, "hi!");

for (@list) {
    if (i_am_a_number($_)) {
        print "$_ is a number!\n";
    } 
}

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      Does this pass muster for zero, signed, and float type numbers? 
      ()-()
 \"/
  `
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        I don't think that passes muster.... Prove me wrong, but I believe that the expression 
        i_am_a_number($_) || i_am_a_number($_)

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        will always be true, no matter what value you choose. You might want to rethink what $_ += 0 does for non numbers, especially ones like "12isnotanumber".

        -Blake

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Re: How to determine a variable value is a number
by Cine (Friar) on Aug 03, 2002 at 01:04 UTC
    Replace ???? with /^[+-]?\d+$. Remove the [+-]? if you dont have a prefix sign.

    T I M T O W T D I
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Re: How to determine a variable value is a number
by Abigail-II (Bishop) on Aug 23, 2002 at 12:56 UTC
    There's also Regexp::Common, which has several regexes for common forms of numbers. Including reals in base 23. (A future version will have regexes for Roman numbers as well).

    Abigail

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