in reply to Is Number

I use the following code. It relies on Perl itself to decide if a string is a number or not. If Perl thinks it's a number, then it returns 1, otherwise zero. Works for big ints too (returns 1 for a big int). 

sub isNumber
{
  defined $_[0] or return 0;
  my $R = 1;
  local $SIG{__WARN__} = sub { $R = 0; };
  return ($_[0] < 0) ? $R : $R;
}

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Re^2: Is Number
by syphilis (Archbishop) on Aug 26, 2022 at 03:53 UTC 
    sub isNumber
{
  defined $_[0] or return 0;
  my $R = 1;
  local $SIG{__WARN__} = sub { $R = 0; };
  return ($_[0] < 0) ? $R : $R;
}

    [download]
    Interesting. I notice that it relies on warnings being enabled ... though that's hardly a criticism of it.
    However, it doesn't aways agree with looks_like_number(): 
    use strict;
use warnings;
use Test::More;

use Scalar::Util qw(looks_like_number);

my $x = 42;
my $y = 'not a number';

cmp_ok(looks_like_number(\$x), '==', isNumber(\$x), 'agrees re ref to 
+number');
cmp_ok(looks_like_number(\$y), '==', isNumber(\$y), 'agrees re ref to 
+non-number');

done_testing();

sub isNumber
{
  defined $_[0] or return 0;
  my $R = 1;
  local $SIG{__WARN__} = sub { $R = 0; };
  return ($_[0] < 0) ? $R : $R;
}

__END__

Outputs:

not ok 1 - agrees re ref to number
#   Failed test 'agrees re ref to number'
#   at IsNumber.pl line 10.
#          got:
#     expected: 1
not ok 2 - agrees re ref to non-number
#   Failed test 'agrees re ref to non-number'
#   at IsNumber.pl line 11.
#          got:
#     expected: 1
1..2
# Looks like you failed 2 tests of 2.

    [download]
    Which one is correct ?

    Cheers,
    Rob
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Re^2: Is Number
by Anonymous Monk on Oct 10, 2022 at 16:25 UTC
[reply]
      oh wait... you did. "it looks like looks_like_number() is better."
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