Zero's vs Null

[fortuneman]

Wrote a little loop to calculate the dec from binary. Problem is that the !$bin matches if $bin is "null" or "zero". I don't want it to match zero. I need a way to get zero to pass through but I'm unsure of an easy way to do this. Additionally, chomp complains too if $bin is null as well. Appreciate any assistance. Thanks.

use strict;

my $bin= shift;
chomp($bin);
my @answer;
my $dec = 0;

if (!$bin|| $bin !~ (/^[01]*$/)) {
        print &quot;Usage: decTobin.pl <decimal value>&quot;;
        exit(0);
}

@answer = split(//, $bin);
find_dec(@answer);
print $dec;

###########
#Find binary position
###########
sub find_dec{
        my $count = 0;
        foreach (reverse(@answer)) {
           $dec = ($dec + ($_ * (2**$count)));
           $count++
        }
}

 

[Coderifous]

Change the condition line to this:

unless ( $bin =~ /[^01]/ || ! defined($_) ) {

--jim

 

[fortuneman]

That still has a problem if you don't pass any arguments. You get a warning when the interpreter tried to do a condition match on a null variable. I've changed the code to the following....it works but I had to turn off warnings....

#!perl

use strict;

my $bin= shift;
my @answer;
my $dec = 0;

if ((!$bin && $bin !~ /0/) || $bin !~ (/^[01]*$/)) {
        print &quot;Usage: binTodec.pl <decimal value>&quot;;
        exit(0);
}

@answer = split(//, $bin);
find_dec(@answer);
print $dec;

###########
#Find binary position
###########
sub find_dec{
        my $count = 0;
        foreach (reverse(@answer)) {
           $dec = ($dec + ($_ * (2**$count)));
           $count++
        }
}

 

[icrf]

Perl's "null" value is undef, and to check that, use the defined() builtin. Zero and the empty string are defined values, undef is the only thing that's not.

----------------------------------------------------------------------------------
...but I'm just a C man trying to see the light

 

[fortuneman]

You're the man!! Thanks. I guess I was thinking that !$var was the same thing but obviously not. Works like a charm...with the warnings on. Thanks again.