Two dimensional array problem

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

Hi all, I want to set up a two dimensional array hold start and stop positions. There are 8 rows and two columns (although there may be more rows in future). I have defined my array as:

  my @Column_Info = { [ 1024, 1067 ],     # Column 1 start stop
                      [ 1068, 1093 ],     # Column 2 start stop
                      [ 1094, 1137 ],     # Column 3 start stop
                      [ 1138, 1163 ],     # Column 4 start stop
                      [ 1164, 1207 ],     # Column 5 start stop
                      [ 1208, 1233 ],     # Column 6 start stop
                      [ 1234, 1277 ],     # Column 7 start stop
                      [ 1278, 1321 ] };   # Column 8 start stop
[download]

When I try and use the array

    my $StartPos = $Column_Info{$Count->[0]};    # Slot to start at
    my $Pos = $StartPos;    # Slot to start at
    my $EndPos = $Column_Info{$Count->[1]};

    open(IN,"cat /tmp/show_library.$$|");
    while (<IN>) {
      $_ =~ s/^ //;
      while ($Pos <= $EndPos) {
        if ($Pos == 1024) {
<snip>
[download]

I get the error

Use of uninitialized value in numeric le (<=) at ./show_library.pl lin
+e 143, <IN> line 69.
Use of uninitialized value in printf at ./show_library.pl line 140, <I
+N> line 70.
[download]

How do I correctly set up and reference this array?
TIA
coec

PS: I have another question about returning a single dimension array from a subroutine but that can wait until later...

Comment on Two dimensional array problem Select or Download Code

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Re: Two dimensional array problem by dpuu (Chaplain) on Jul 21, 2002 at 03:32 UTC
I think your problems stem from your use of curly brackets when you define your array. @column_info is a list containing exactly one element -- a reference to a rather strange hash. To see what you're doing wrong, try adding: `use Data::Dumper; print Dumper(\@Column_Info);` [download] If you get rid of the curlies (use round parentheses instead), then you'll be able to reference the array as: `my @array = ( [0,0], [0,1], [1,0], [1,1] ); for (my $x=0; $x<4; $x++) { for (my $y=0; $y<2; $y++) { printf "%d,%d = %n", $x, $y, $array[$x][$y]; } }` [download]	[reply] [d/l] [select]
Re: Two dimensional array problem by Nitrox (Chaplain) on Jul 21, 2002 at 03:39 UTC
Follow the advice in the previous post regarding the curly brackets and then change your reference's to: `my $StartPos = $Column_Info[$Count][0];` [download] -Nitrox	[reply] [d/l]
Re: Two dimensional array problem by flocto (Pilgrim) on Jul 21, 2002 at 09:30 UTC
> How do I correctly set up and reference this array? If I was you I'd rather use an array reference. There is no need to do this, but it feels more appropriate. Your array could look like this: `my $array_ref = [ [ 123, 456 ], [ 234, 567 ], [ 345, 678 ] ];` [download] This array reference can be used in a variety of ways, but the most obvious are these: `my $pos = $array_ref->[$x][$y]; my $row = $array_ref->[$x]; my $column = $row->[$y];` [download] Regards, -octo	[reply] [d/l] [select]