Parsing and scoring an Array of Arrays

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

Hi monks!

I am having a problem with my OOP data structure! Basically, I have an array that holds arrays of data. This data is just 1's and 0's.
Like This:
-----------
array cell 0 = (1,0,0,0,1,1,0)
array cell 1 = (0,0,0,1,1,1,1,0,0,1,1,1)
array cell 2 = (1,1,0,1,1,1,1,0,0,1,1,1)
etc...

My constructor looks something like this:

sub new
 {
   my ($class) = @_;
   my $self =  {
                _length          => "",
                _score           => [ [],[] ],
                _coordinates     => [],
                };
 
    bless {$self,$class};
 } # END "new" method
[download]

What I need to do is go through each data array in my @{$self->_score}[] array and output a comma-delimited list of coordinates whenever a string of 1's is encountered...

Like this:
if @{$self->_score}index = (1,1,1,0,0,1,1,0)
then i want
@($self->_coordinates}index = "0-2,5-6"

Easy Right?

But why can't I just do this:

sub findcoordinates
   {
     my ($self) = @_;
     my $first;
     my $last;
     for (my $i=2;$i <= 5;$i++) 
       {   
         my $base = 0;
         while($base <= (($self->{_length})-$i)) 
           {
            if (@{$self->{_score}[$i][$base]} = "1")
              {
               $first = $base;
               while (@{$self->{_score}[$i][$base]} ne "0") 
                {
                  $last = $base;
                  $base++; 
                } 
                  @{$self->{_coordinates}[$base] =  @{$self->{_coordin
+ates}[$base] + "$first-$last";
               }
              else
               {
                $base++;
               }
           }  
       }
  } #END findcoordinates method
[download]

What this all means is that IF the Data cell = '1', continue to move down the array until the data cell isn't equal to '1' anymore. Then print out the first cell # and the last one parsed like this: "3-5" or something.
Problem is I always get a Can't use undefined value as an array reference error? Why do i get this error? Any suggestions as to a better way to accomplish my monk-ish task?

Comment on Parsing and scoring an Array of Arrays Select or Download Code

Replies are listed 'Best First'.
Re: Parsing and scoring an Array of Arrays by chromatic (Archbishop) on Aug 09, 2001 at 00:56 UTC
My guess is this code: `while (@{$self->{_score}[$i][$base]} ne "0") { $last = $base; $base++; }` [download] How many items are in the array at $i? Your code never checks. It keeps incrementing $base. Eventually, it's going to run out of items, and Perl will happily attempt to oblige you by autovivifying a new array entry at the new position. It won't be an array reference, though, and there's your error. As a side note, be careful with your comparisons. You almost certainly don't want to say `if ($x = 1) {`...	[reply] [d/l] [select]
Re (tilly) 2: Parsing and scoring an Array of Arrays by tilly (Archbishop) on Aug 09, 2001 at 09:07 UTC
ObRandomTip: To avoid making the mistake: `if ($x = 1) { # etc }` [download] get into the habit of trying to put the variables on the right, not the left. It looks strange, but: `if (1 = $x) { # etc }` [download] is likely to give you a much more informative error message. (This habit will serve you in good stead in quite a few languages, not just Perl.)	[reply] [d/l] [select]
Re: Re: Parsing and scoring an Array of Arrays by mr_dont (Beadle) on Aug 09, 2001 at 04:16 UTC
Chromatic, I think that you are right... Thanks, Mr. Don't!	[reply]
Re: Parsing and scoring an Array of Arrays by dragonchild (Archbishop) on Aug 09, 2001 at 00:49 UTC
I'd reccomend putting a bunch of print statements or using the debugger. Find out where the actual bomb is happening. :) ------ /me wants to be the brightest bulb in the chandelier! Vote paco for President!	[reply]