So I'm the resident Perl Answer Guy at my orkplace (not that I'm the best Perl hacker here, but those better than I are either busy doing other stuff, like running the network, or just don't like answering questions). I got an interesting one the other day, and it's still bugging me.

My colleague had a 2d array simulating a textmode screen. 22 rows, 80 columns; however, he wanted to write to the "screen" first, then worry about over-long lines, so each row could have more than 80 chars in it. He had it set up like so:

$vscr[$x][$y];

[download]

The question was, how do you traverse this array row by row? The obvious answer,

foreach my $x (@vscr) {
  foreach my $y (@$x) {
    &do_stuff($y);
  }
}

[download]
traverses the screen in the wrong order.

My first suggestion was to switch the order of x and y in the array; this isn't quite as intuitive for accesses, but makes the obvious traversal DTRT. But this bugged me: after all, TMTOWTDI, right? So I came up with this:

foreach my $row (0..21) {
  foreach my $col (@vscr) {
    &do_stuff($col[$row]);
  }
}

[download]
(At this point, he has changed the order of x and y in the array, so this code never got used, which means it's untested and probably broken.)

This isn't so much worse than the obvious nested foreach approach, but it bugs me that the number of rows is hard coded. Is there a more general way to do this that's still fairly clean?

In reply to Fun with two-dimensional arrays by FoxtrotUniform

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