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

Hi -- I grabbed the is_numeric function from perfaq4. Either I am using it wrong, or it doesn't work. The following code asserts that undef and fish are numeric. What's going wrong? Thanks -- nop 
use POSIX qw(strtod);
use strict;

foreach (undef, qw(4 0 fish)) {
    print $_ , " is numeric? ", is_numeric($_), "\n";
}

sub getnum {
    my $str = shift;
    $str =~ s/^\s+//; $str =~ s/\s+$//; $! = 0;
    my($num, $unparsed) = strtod($str);
    if (($str eq '') || ($unparsed != 0) || $!) {return;} else {return
+ $num;} 
} 

sub is_numeric { defined scalar &getnum }

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Re: is_numeric from perlfaq4
by Abigail-II (Bishop) on Oct 07, 2002 at 18:02 UTC
    You never called the function getnum. All you did was returning whether the sub getnum was defined. Which it was.

    You didn't copy the is_numeric function correctly from the faq. It should be: 

    sub is_numeric {defined getnum $_ [0]}

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    Abigail

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Re: is_numeric from perlfaq4
by thelenm (Vicar) on Oct 07, 2002 at 18:06 UTC
    Are you using an older version of Perl? In perlfaq4 for 5.6.1 and 5.8.0, the is_numeric function looks like this (slightly different), and works correctly for your example: 
    sub getnum {
    use POSIX qw(strtod);
    my $str = shift;
    $str =~ s/^\s+//;
    $str =~ s/\s+$//;
    $! = 0;
    my($num, $unparsed) = strtod($str);
    if (($str eq '') || ($unparsed != 0) || $!) {
        return undef;
    } else {
        return $num;
    }
}

sub is_numeric { defined getnum($_[0]) }

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    -- Mike

    --
    just,my${.02}

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Re: is_numeric from perlfaq4
by fglock (Vicar) on Oct 07, 2002 at 18:08 UTC

    It works if you use:

    sub is_numeric { defined scalar getnum(@_) }
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