如何判断变量在 Perl 中是否有数值？

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))
{ ... }

would be ideal. A technique that won't throw warnings when the -w switch is being used is certainly preferred.

转载于:https://stackoverflow.com/questions/12647/how-do-i-tell-if-a-variable-has-a-numeric-value-in-perl

Answer 1

Use Scalar::Util::looks_like_number() which uses the internal Perl C API's looks_like_number() function, which is probably the most efficient way to do this. Note that the strings "inf" and "infinity" are treated as numbers.

Example:

#!/usr/bin/perl

use warnings;
use strict;

use Scalar::Util qw(looks_like_number);

my @exprs = qw(1 5.25 0.001 1.3e8 foo bar 1dd inf infinity);

foreach my $expr (@exprs) {
    print "$expr is", looks_like_number($expr) ? '' : ' not', " a number\n";
}

Gives this output:

1 is a number
5.25 is a number
0.001 is a number
1.3e8 is a number
foo is not a number
bar is not a number
1dd is not a number
inf is a number
infinity is a number

see also:

[perldoc Scalar::Util][1]
[perldoc perlapi][2]