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

I am trying to come up with a set of regular expressions that can go into the code I have written to scan the data at the end of the code and tell me how many positive, negative, and 0 integers. 

 
#!/usr/bin/perl
use strict;
use warnings;
my ( $ctrP, $ctrN, $ctrZ ) = ( 0, 0, 0 );
while( my $num = <DATA> ) {
        chomp($num);
        ## print "num=[$num]\n";
        if ( $num =~ /REGEX FOR POSITIVE/ ) {
                $ctrP++;
        }
        elsif ( $num =~ /REGEX FOR NEGATIVE/ ) {
                $ctrN++;
        }
        else {
                $ctrZ++;
        }
}
printf("freq(Z+):%8s\n", $ctrP );
printf("freq(Z-):%8s\n", $ctrN );
printf("freq(0):%9s\n", $ctrZ );
printf("Total:%11s\n", ($ctrP+$ctrN+$ctrZ) );
exit;
__DATA__
29
-62
696
242
78
-564
0
45
855
22
-67

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Content above restored by GrandFather

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Re: Regex to find the number of positive, negative, and 0 integers within a data set
by BrowserUk (Patriarch) on Feb 28, 2017 at 20:46 UTC

    Firing up the regex engine to make a simple numeric comparison is like using a blunderbus to swat flies.

    This is probably an order of magnitude more efficient:

    #! perl -slw
use strict;

my @counts;

++$counts[ 1+ ( $_ <=> 0 ) ] while <DATA>;

printf "Neg:%d Zero:%d Pos:%d\n", @counts;


__DATA__
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    Output:

    C:\test>1183178.pl
Neg:3 Zero:1 Pos:7

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    Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
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    In the absence of evidence, opinion is indistinguishable from prejudice.
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Re: Regex to find the number of positive, negative, and 0 integers within a data set
by 1nickt (Canon) on Feb 28, 2017 at 17:48 UTC

    Hi neveraloneneverapart, welcome to the Monastery and to Perl, the One True Religion.

    Assuming every line in __DATA__ is known to contain a number, I would use a hash to count results and a numeric comparison: 

    use strict; use warnings; use feature 'say';
use Data::Dumper;

my %results;

while (<DATA>) {
    chomp;
    $results{'zero'}++ if $_ == 0;
    $results{'pos'}++ if $_ > 0;
    $results('neg'}++ if $_ < 0;
}

print Dumper \%results;

    [download]

    Alternatively, to see if a string is a number, see Scalar::Util::looks_like_number().

    If you really wanted to, for a regexp for Latin integers, you could use $num =~ m/  \A -? [0-9]+ \z /x;

    To capture the sign (or nothing) and the digits and then be able to use them: 

    if ($num =~ m/  \A (-?) ([0-9]+) \z /x ) {
    my $sign = $1;
    my $digits = $2;
    ...
}

    [download]

    Also see Regexp::Common

    Hope this helps!

    edit: removed unnecessary escape slash

    The way forward always starts with a minimal test.
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      Thanks for the post! I came up with the regex for the positive ints. 

      while( my $num = <DATA> ) {
        chomp($num);
        ## print "num=[$num]\n";
        if ( $num =~ /^[1-9]\d*$/ ) {
                $ctrP++;
        }

      [download]

      I would like for it to be in regular expressions so that I can learn how to use them properly. I am having trouble so that the regex for the negative ints finds only negative ints.

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