uninitialized value seems initialized

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

Hi Monks!

I have some code (listed below) within a module that does behave as it should but leads to error messages:

Use of uninitialized value in subtraction (-) at /usr/lib/perl5/site_perl/5.8.5/Chemistry/File/AMBERprmtop.pm line 109, <GEN0> line 1044. at /usr/lib/perl5/site_perl/5.8.5/Chemistry/File/AMBERprmtop.pm line 109

I cannot see what value is not initialized: $n and $r are initialized in line 104, $respt[$r] is part of @respt which is initialized in line 80.

Am I missing something? (Sure, I do...) Any hints are welcome! Thanks for your help.

 80:  my ($lines, @masses, @names, @charges, @resnames, @respt, $symbo
+l);
 99:  for ($lines=$pointers{respt}[0]; $lines<=$pointers{respt}[1]; $l
+ines ++) {
100:    push @respt, (unpack (("A8" x (length($file[$lines]) / 8)), $f
+ile[$lines]));
101:  }
104:  my ($n, $r) = (0, 0);
105:  for $n (0 .. $#masses) {
109:    if ($n == ($respt[$r]-1)) {
110:      $r++;
111:    }
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Re: uninitialized value seems initialized by Corion (Patriarch) on Aug 04, 2006 at 09:18 UTC
You're confusing declaration and initialization. `@respt` is declared in line 80, but likely, not all elements of `@respt` are initialized in line 99, or rather, not enough elements. To further debug this, print out the number of elements in `@respt`: `#line 102 print "Elements in \@respt: ", scalar @respt;` [download]	[reply] [d/l] [select]
Re^2: uninitialized value seems initialized by Fisch (Novice) on Aug 04, 2006 at 09:40 UTC
You are right! My @respt is missing one entry. Thanks for your immediate response and help!	[reply]