To check if a variable is a positive integer, do you recommend to use Scalar::Util::LooksLikeNumber or one of the suggested simple code without installing a new module could be used?

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Hello carolw,

To check if a variable is a positive integer, do you recommend to use Scalar::Util::LooksLikeNumber ... ?

I assume you mean Scalar::Util::looks_like_number, but that won’t distinguish between positive integers and other types of numbers, such as floating-point numbers and negative integers.

It’s possible that the simple regex /^\+?\d+$/ is all you need, but that won’t recognise positive integers such as 0xDEADBEEF and 1e6. For a comprehensive solution, the Data::Types module has the is_whole function:

use strict;
use warnings;
use Data::Types ':whole';

for (0, -1, 17, 1.25, 1e6, 062, 0xDEADBEEF, 4.0, 5.)
{
    printf "%10s: %s\n", $_, is_whole($_) ? 'yes' : 'no';
}
[download]

Output:

23:51 >perl 989_SoPW.pl
         0: yes
        -1: no
        17: yes
      1.25: no
   1000000: yes
        50: yes
3735928559: yes
         4: yes
         5: yes

23:51 >
[download]

For additional options, see How-do-I-determine-whether-a-scalar-is-a-number-whole-integer-float of perlfaq4 cited by bronto further down in this thread.

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Update 1: Escaped the first + in the regex:

/^\+?\d+$/
  ^
[download]

Update 2: Actually, the simple regex does recognise 0xDEADBEEF and 1e6 because Perl converts them to standard decimal form before the regex is applied.

Hope that helps,

Athanasius <°(((>< contra mundum

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