Uninit Value - Hash Value Compare

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

Hey, have what is probably a simple question, but I'm struggling a bit and I've checked what I know to check. I have a hash to sort by value, and I'm getting "Use of uninitialized value in string comparison (cmp) at blahblah line 66." when I sort it. But I've checked and don't seem to have any empty values. Hopefully I don't make a syntax error, I have to type it because it's in a secure system so I can't copy/paste and I had to anonymize function names and hash names and stuff. It does run, and it sorts the hashes fine. Code:

#!/usr/bin/perl
use Win32;
use strict;
use warnings;
use v5.10.10;
use Data::Dumper;
user constant {
    DEBUG => 1,
}

my %hash;
my $counter;
#hash has stuff put in it here
$counter = &compare_hash(\%hash);

sub compare_hash{
    my $hashRef = shift;
    my $hash = %$hashRef;
    my $counter = 0;

    print Dumper(\%hash); #searching for undef or blank ('') values in
+ the dump output comes up empty
    print "$_ has undef as value\n" for grep {not defined $hash{$_}} k
+eys %hash #this comes up empty, thanks to Corion for the 
    #suggestion

    foreach my $key (sort { $hash{$a} cmp $hash{$b} } keys %hash){ #th
+is is line 66
        #do something
        #print and check and stuff on $hash{$key}
        ++$counter;
    }

    return $counter;
}
[download]

Thanks in advance.

Comment on Uninit Value - Hash Value Compare Download Code

Replies are listed 'Best First'.
Re: Uninit Value - Hash Value Compare by choroba (Cardinal) on Nov 05, 2020 at 15:59 UTC
That's not the code you're running. It doesn't even compile! There is a missing semicolon on the grep line. Also, note that `my $hash = %$hashRef;` [download] is most probably wrong, did you mean `my %hash = %$hashRef;` [download] instead? Your version populates a scalar variable $hash with the size of the hash and the rest of the code operates on the %hash variable from the outer scope. `map{substr$_->[0],$_->[1]\|\|0,1}[\\|\|{},3],[[]],[ref qr-1,-,-1],[{}],[sub{}^ARGV,3]`	[reply] [d/l] [select]
Re^2: Uninit Value - Hash Value Compare by kchinger (Initiate) on Nov 05, 2020 at 16:47 UTC
yeah, as I mentioned, I have to re-type the code, and I had to remove code/anonymize variable names and stuff because it's in a secure area that I can't copy/paste from and can't get on the internet on. And yes, I actually have my %hash = %$hashRef; Just a typo in what I put here, sorry. I think the missing semicolon it's getting away with because it's the last line in the block, that was that way in my working code. I fixed it for accuracy in my code, no changes, obviously. Sorry. I can try a better way to get it out of the system and anonymize it better so it actually runs fully if I need to.	[reply]
Re^3: Uninit Value - Hash Value Compare by AnomalousMonk (Archbishop) on Nov 05, 2020 at 18:07 UTC
For the importance of and tips on constructing a small, executable code example, see Short, Self-Contained, Correct Example. Perhaps also take a look at I know what I mean. Why don't you? Give a man a fish: `<%-{-{-{-<`	[reply] [d/l]
Re: Uninit Value - Hash Value Compare by kchinger (Initiate) on Nov 05, 2020 at 19:54 UTC
I apologize for wasting everyone's time. It was right in front of me, and I ended up fixing the issue by attempting to anonymize, which is why you couldn't find it. Before I changed names, I had something more like below: `foreach my $key (sort { $hashNew{$a} cmp $hashOld{$b} } keys %hashOld)` In making the short one I changed the hash names, and made them the same, because I knew that's what I was supposed to do, but didn't notice that I had the wrong variables. My hashes were similar enough that I only got a few errors, instead of thousands, because the key existed in both in most cases	[reply] [d/l]