Use of uninitialized value in addition (+)

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

What does this error mean?

Use of uninitialized value in addition (+) at lib.pl line 13, <STDIN> line 1.

I've initialized my values so I'm not sure why the error...

Here is the full code (it is a library file):

#!/usr/bin/perl
use strict;
use warnings;
my $line;
sub calcsum {
   my @funcArray = @_;
     my $funcSum = 0;
     my $funcArr = 0;
   my $arrcount = scalar(@_);
   foreach my $line (@funcArray) {
     $funcSum += $line;
     } 
   return ($funcSum);
   }
[download]

Here's the main file:

#!/usr/bin/perl
use strict;
use warnings;

require 'lib.pl';

my @userArray = <STDIN>;

my $sum = calcsum(my $funcSum);

print "Sum $sum\n";
[download]

I'm still learning so please be kind. I've tried moving the "my $line;" after the sub line and it didn't make a difference.

Thanks.

Comment on Use of uninitialized value in addition (+) Select or Download Code

Replies are listed 'Best First'.
Re: Use of uninitialized value in addition (+) by vinoth.ree (Monsignor) on Apr 08, 2009 at 03:31 UTC
You have declared the variable `$funcSum` but not assigned any value in it, So when you call the function `calcsum()` with this argument it passes the undef value, So in function definition you are getting the error message	[reply] [d/l] [select]
Re^2: Use of uninitialized value in addition (+) by Anonymous Monk on Apr 08, 2009 at 04:20 UTC
Monks rule! Thanks	[reply]
Re: Use of uninitialized value in addition (+) by Anonymous Monk on Apr 08, 2009 at 03:10 UTC
This `\|\|\|\|\|\|\|\|\|\|\|\|\| VVVVVVVVVVVVV my $sum = calcsum(my $funcSum);<<<<< ^^^^^^^^^^^^^ \|\|\|\|\|\|\|\|\|\|\|\|\|` [download] is equivalent to `calcsum(undef);`	[reply] [d/l]
Re^2: Use of uninitialized value in addition (+) by Anonymous Monk on Apr 08, 2009 at 04:21 UTC
Monks rule! Thanks.	[reply]
Re: Use of uninitialized value in addition (+) by ELISHEVA (Prior) on Apr 08, 2009 at 04:05 UTC
This one confused me a lot too when I was first learning Perl! You are probably thinking "yeah, sure - I know I passed an undefined variable to `calcsum`, but why is it causing a problem?! After all I passed "nothing" to `calcsum`! My guess is that you think you are passing an undefined "array" when actually you are passing a list with a single value `undef` in it: `(undef)`. Thus your `foreach` loop is equivalent to: `my @funcArray = (undef) #my @funcArray = @_; my $funcSum = 0; my $funcArr = 0; my $arrcount = 1; #my $arrcount = scalar(@_); foreach my $line ((undef)) { #foreach my $line (@funcArray) $funcSum += $line; }` [download] Who'd ever thought - so much confusion from nothing? Best, beth	[reply] [d/l] [select]
Re: Use of uninitialized value in addition (+) by toolic (Bishop) on Apr 08, 2009 at 17:18 UTC
Since others have helped solve your problem, I thought I'd point out that the List::Util core module has a `sum` function equivalent to your `calcsum` function: `use strict; use warnings; use List::Util qw(sum); my @userArray = <STDIN>; my $sum = sum(@userArray); print "Sum $sum\n";` [download]	[reply] [d/l] [select]