Re: Multi-Dimensional Arrays and Array References

[Marshall]

Here are some more examples for you...

#!/usr/bin/perl
use strict;
use warnings;

# simple 1D arrays:

my @rowx = (1,2,3,4);
my @rowy = qw (a b c);

# A 2D array is an array of references to 1D arrays:
# Note that Perl 2D arrays do not need to have the same
# number of elements on each row!

my @twoD = (\@rowx, \@rowy);

foreach my $rowref (@twoD)
{
    print "@$rowref\n";
}

# prints
# 1 2 3 4
# a b c


# this can be a bit confusing...
# In the first print, Perl knows that $twoD[0][1] means
#    an array element of @twoD, not be confused with
#    perhaps a simple scalar of the same name!
#
# In the second print, we get the value of $twoD,
#    a simple scalar


my $twoD = "asdf";

print "$twoD[0][1]\n";  # prints 2

print "$twoD\n";        # prints asdf


# In general, DO NOT use the same variable name for
# two different sigils!  Many things are "legal" in Perl
# that you should not do!

Update: You will notice that in my foreach loop, I used the name "rowref" instead of just "row". Perl wouldn't care. But naming the iteration variable like this helps me to remind myself to dereference that thing. YMMV.

[GrandFather]

Note that Perl 2D arrays do not need to have the same number of elements on each row!

nor even the same type of data:

use strict;
use warnings;

package PrintMe;

use overload '""' => sub {return $_[0]{str};};

sub new {
    return bless {str => $_[1]}, $_[0];
}

package main;

my @mixedTable = (
    [1 .. 5],
    {a => 1, b => 2, wibble => 'plop'},
    PrintMe->new("The quick brown fox")
    );

for my $row (@mixedTable) {
    if ('ARRAY' eq ref $row) {
        print "@$row\n";
    } elsif ('HASH' eq ref $row) {
        print join ', ', map{"$_ => $row->{$_}"} sort keys %$row;
        print "\n";
    } else {
        print "$row\n";
    }
}

Prints:

1 2 3 4 5
a => 1, b => 2, wibble => plop
The quick brown fox