Re: Multidimensional Arrays

[Anonymous Monk]

in reply to Multidimensional Arrays

my @row0 = (1, 0, 0);
my @row1 = (0, 1, 0);
my @row2 = (0, 0, 1);
my @arr = ( \@row0, \@row1, \@row2 );
for ( $i = 0; $i < 3; $i++ ) {
        for ( $j = 0; $j < 3; $j++ ) {
                print "arr[$i][$j] = $arr[$i][$j]\n";
        }
} # works perfectly
print "*" x 80, "\n";
my @another = \$arr[1];
for ( $i = 0; $i < 3; $i++ ) {
        print "another[$i] = $another->[$i]\n";
} # while this loop prints blanks

what am i doing wrong ?

[chb]

You could try:

my @another = @{$arr[1]};
for ( $i = 0; $i < 3; $i++ ) {
        print "another[$i] = $another[$i]\n";
} 

using an array to hold the row, or:

my $another = $arr[1];
for ( $i = 0; $i < 3; $i++ ) {
        print "another[$i] = $another->[$i]\n";
} 

using a ref to the row. You should also consider use strict;, BTW...

[wfsp]

my @another = \$arr[1];

@another has a single element - a reference to a reference to an array.

Try:

${${$another[0]}}[$i]

Update: fixed typo

[chb]

This works, too:

@{${$another[0]}}[$i]

I think ist is a little bit clearer (from in to out): 1. fetch array element 0, 2. dereference, 3. treat it like an array, 4. fetch via [$i].

But this all looks really ugly. It would be better to fix the strange assignment to @another than to use such a complicated expression just to fetch a value...

[wfsp]

You're right.

I find Perl's data structures very useful but often get into a tangle with them. The main reason I had a go at the OP's question was to see if I could fathom it out. I was so pleased when I actually got something to work I couldn't resist the urge to show off!

I must now confess that I dereferenced it in stages first using temps. This is what I usually do myself if only so that I can still understand it the following day.

++ to you for being helpful rather than trying to be clever. My bad!