Recursive Hilbert Curve generator

hilbert-curve.pl

#!/usr/bin/env perl
# http://www.fundza.com/algorithmic/space_filling/hilbert/basics/
# http://www.soc.napier.ac.uk/~andrew/hilbert.html
use strict;
use warnings;

sub hilbert {
    my ($n, $x, $y, $xi, $xj, $yi, $yj, $mn) = (@_, qw(0 0 1) x 2, $_[0]);
    return !$n
        ? [
            map { (2 ** $mn) * $_ - 0.5 }
            ($y + ($yi + $xi)/2, $x + ($yj + $xj)/2)
        ] : (
            hilbert($n-1, $x,               $y,             $yi/2, $yj/2,   $xi/2,  $xj/2, $mn),
            hilbert($n-1, $x+$xi/2,         $y+$xj/2 ,      $xi/2, $xj/2,   $yi/2,  $yj/2, $mn),
            hilbert($n-1, $x+$xi/2+$yi/2,   $y+$xj/2+$yj/2, $xi/2, $xj/2,   $yi/2,  $yj/2, $mn),
            hilbert($n-1, $x+$xi/2+$yi,     $y+$xj/2+$yj,  -$yi/2,-$yj/2,  -$xi/2, -$xj/2, $mn),
        );
}

printf "%d,%d\n", @$_ for hilbert($ARGV[0] || 1);