Matrix Reference

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

Hello again, I have built a matrix of say 5 X 5, and I would like to have the ability to reference any col and row I choose (ie. $matrix_ref->[5][3]=$foo) this is what i have for code:

my $matrix_ref;

    for(0..$length2
    {
        for(0..$length1)
    {
        @test = populate($length1);
            $matrix_ref->[$row][$col] = \@test;
        }
    }
    
    for(0..$length2)
    {
    print "[";
    
        for(0..$length1)
        {   
            print "$matrix_ref->[$row][$col][$_] ";
        }
        print "] \n\n";
    
    }
}

sub populate 
{ 
   my $elements = shift;
   my @ary;
       push @ary, $matrix[$element];
       $element ++;
   return @ary;
}
[download]

What is the best way to access a specific location in the array to make changes, and/or check a value?

Thanks for the help

Edit Masem 2002-03-01 - CODE tags

Comment on Matrix Reference Select or Download Code

Replies are listed 'Best First'.
Re: Matrix Reference by jmcnamara (Monsignor) on Mar 01, 2002 at 14:55 UTC
If you are specifically interested in matrices have a look at Math::MatrixReal and in particular the `assign()` method. This will also take care of the pretty-printing. This is a neat module. From the pod (but not directly related to the question): `$matrix = Math::MatrixReal->new_from_string(<<'MATRIX'); [ 1 0 0 0 0 0 1 ] [ 0 1 0 0 0 0 0 ] [ 0 0 1 0 0 0 0 ] [ 0 0 0 1 0 0 0 ] [ 0 0 0 0 1 0 0 ] [ 0 0 0 0 0 1 0 ] [ 1 0 0 0 0 0 -1 ] MATRIX` [download] If on the other hand you just want to deal with a 2-D array of data have a look a perllol. -- John.	[reply] [d/l]
Re: Matrix Reference by ton (Friar) on Mar 01, 2002 at 19:24 UTC
I have to admit, I clicked on this node because I wanted to see a reference to "The Matrix", e.g. "There is no spoon." But now that I've looked at your code, I thought I'd give some feedback: use strict. Really. A lot of problems will become apparent if you do. In populate, you use $element without declaring it (you declare $elements.) In populate, you use $matrix without declaring it. So `$matrix[$element]` will always return 0. Within the main code, you continuously use $row and $col without ever changing them. So you are always indexing at 0, 0. (I assume $length1 and $length2 were initialized elsewhere, otherwise they too are always equal to 0). Even if $row and $col changed, setting `$matrix_ref->[row][$col]` to \@test is setting all elements to be a reference to the same array (@test). I'm pretty sure that's not what you want. Items 2, 3, and 4 would have been immediately obvious had you used strict. -Ton ----- Be bloody, bold, and resolute; laugh to scorn The power of man...	[reply] [d/l] [select]