How do I tell if a variable has a numeric value in Perl?

Question

Is there a simple way in Perl that will allow me to determine if a given variable is numeric? Something along the lines of:

if (is_number($x))
{ ... }


        

Answer 1

Try this:

If (($x !~ /\D/) && ($x ne "")) { ... }

Answer 2

A simple (and maybe simplistic) answer to the question is the content of $x numeric is the following:

if ($x  eq  $x+0) { .... }

It does a textual comparison of the original $x with the $x converted to a numeric value.

Answer 3

You can use Regular Expressions to determine if $foo is a number (or not).

Take a look here: How do I determine whether a scalar is a number

Answer 4

rexep not perfect... this is:

use Try::Tiny;

sub is_numeric {
  my ($x) = @_;
  my $numeric = 1;
  try {
    use warnings FATAL => qw/numeric/;
    0 + $x;
  }
  catch {
    $numeric = 0;
  };
  return $numeric;
}

Answer 5

The original question was how to tell if a variable was numeric, not if it "has a numeric value".

There are a few operators that have separate modes of operation for numeric and string operands, where "numeric" means anything that was originally a number or was ever used in a numeric context (e.g. in $x = "123"; 0+$x, before the addition, $x is a string, afterwards it is considered numeric).

One way to tell is this:

if ( length( do { no warnings "numeric"; $x & "" } ) ) {
    print "$x is numeric\n";
}

If the bitwise feature is enabled, that makes & only a numeric operator and adds a separate string &. operator, you must disable it:

if ( length( do { no if $] >= 5.022, "feature", "bitwise"; no warnings "numeric"; $x & "" } ) ) {
    print "$x is numeric\n";
}

(bitwise is available in perl 5.022 and above, and enabled by default if you use 5.028; or above.)

Answer 6

Usually number validation is done with regular expressions. This code will determine if something is numeric as well as check for undefined variables as to not throw warnings:

sub is_integer {
   defined $_[0] && $_[0] =~ /^[+-]?\d+$/;
}

sub is_float {
   defined $_[0] && $_[0] =~ /^[+-]?\d+(\.\d+)?$/;
}

Here's some reading material you should look at.