sub min {(sort {$a<=>$b} @_ )[0];}
sub max {(sort {$a<=>$b} @_ )[-1];}

##</code><code>##

 
sub min_max {
    my( $min, $max ) = ( 1e-308, 1e308 );
    for(@_){
        $min = $_ if $_ < $min;
        $max = $_ if $_ > $max;
    }
    return ($min, $max);
}

##</code><code>##

#! perl -slw
use strict;
use GD;
use GD::Polyline;
use Data::Dumper;

use constant PI => 3.14159265359;

sub Turtle {
	my( $dir, $polyline, $xy ) = ( 0, new GD::Polyline, [ 0, 0 ] );
	return sub {
		return $polyline unless @_;
		$dir += shift||0;
		my $dist = shift||0;
		$xy->[0] += $dist*sin(PI*$dir/180);
		$xy->[1] += $dist*cos(PI*$dir/180);
		$polyline->addPt( @$xy );
		return;
	};
}

sub plotxy {
	my( $polyline, $file, $scale ) = @_;

	$polyline->scale( $scale, $scale, 0, 0 ) if $scale;
	my( $centre_x, $centre_y ) = $polyline->centroid;
	$polyline->offset( int($centre_x+10), 10 + -int(2*$centre_y)  );

	my( $width, $height ) = ($polyline->bounds)[2,3];

	my $image = new GD::Image( $width + 10, $height + 10 );
	my $white = $image->colorAllocate(255,255,255);
	my $black = $image->colorAllocate(0,0,0);
	$image->transparent($white);
	$image->interlaced('true');
	$image->polyline( $polyline, $black );
	open(IMG, ">$file");
	binmode IMG;
	print IMG $image->jpeg;
}

sub koch {
	my ($turtle, $d, $level) = @_ ;
	if ($level==0) {$turtle->(0,$d); return 1;}
	$turtle->(  0,0); koch($turtle,$d/3,$level-1);
	$turtle->(-60,0); koch($turtle,$d/3,$level-1);
	$turtle->(120,0); koch($turtle,$d/3,$level-1);
	$turtle->(-60,0); koch($turtle,$d/3,$level-1);
}

my $turtle = Turtle();
map {$turtle->(120, 0); koch($turtle, 170, 4);} 0..2;

plotxy($turtle->(), 'koch.jpg', 3);


# Minkowski Island
sub minkowski {
	my ($turtle, $d, $level) = @_ ;
	if ($level==0) {$turtle->(0,$d); return 1;}
	minkowski($turtle,$d/4,$level-1);
	$turtle->(-90,0); minkowski($turtle,$d/4,$level-1);
	$turtle->( 90,0); minkowski($turtle,$d/4,$level-1);
	$turtle->( 90,0); minkowski($turtle,$d/4,$level-1);
	minkowski($turtle,$d/4,$level-1);
	$turtle->(-90,0); minkowski($turtle,$d/4,$level-1);
	$turtle->(-90,0); minkowski($turtle,$d/4,$level-1);
	$turtle->( 90,0); minkowski($turtle,$d/4,$level-1);
}

$turtle = Turtle();
map {$turtle->(90,0); minkowski($turtle, 150, 3);} 0..3;

plotxy($turtle->(), 'minkowski.jpg', 2);

# Dragon Curve
sub dragon1 {
	my ($turtle, $d, $level) = @_ ;
	if ($level==0) {$turtle->(0,$d); return 1;}
	dragon($turtle,$d*0.707,$level-1);
	$turtle->(-90,0); dragon1($turtle,$d*0.707,$level-1);
}
sub dragon {
	my ($turtle, $d, $level) = @_ ;
	if ($level==0) {$turtle->(0,$d); return 1;}
	dragon($turtle,$d*0.707,$level-1);
	$turtle->(90,0); dragon1($turtle,$d*0.707,$level-1);
}

$turtle = Turtle();
dragon($turtle, 150, 12);

plotxy($turtle->(), 'dragon.jpg', 2);


##</code><code>##

    $xy->[0] += $dist*sin(PI*$dir/180);
    $xy->[1] += $dist*cos(PI*$dir/180);

##</code><code>##

my %sin_d; sub sin_d{ my $d=shift; $sin_d{$d} || ( $sin_d{$d} = sin(PI*$d/180) ); }
my %cos_d; sub cos_d{ my $d=shift; $cos_d{$d} || ( $cos_d{$d} = cos(PI*$d/180) ); }

....

		$xy->[0] += $dist * sin_d($dir);
		$xy->[1] += $dist * cos_d($dir);
...