Oooh! Pretty! That's a fractal right? What's it called?

use strict;
use Tk;

my $phi = 0;
my $thisX = 185;
my $thisY = 500;
my $nextX = 185;
my $nextY = 500;

my $mw = MainWindow->new;
$mw->geometry( "700x700" );
my $c1 = $mw->Canvas( -background => 'black',
                      -height => 700,
                      -width => 700)
  ->pack;

use constant PRINT => 'P';
use constant LEFT  => '<';
use constant RIGHT => '>';

my $ax = "P>" x 4 . "P";
$ax =~ s/P/P<P>P>P<P/g for 1 .. 4;

for (split //, $ax)
  {
    if ($_ eq RIGHT)
      {
        # rotate right
        $phi += 90;
        $phi -= 360 if $phi >= 360;
      }

    elsif ($_ eq LEFT)
      {
        # rotate left
        $phi -= 90;
        $phi += 360 if $phi < 0;
      }

    elsif ($_  eq PRINT)
      {
        # print
        $thisX = $nextX;
        $thisY = $nextY;

        if    ($phi ==   0) { $nextX += 4 }
        elsif ($phi ==  90) { $nextY -= 4 }
        elsif ($phi == 180) { $nextX -= 4 }
        elsif ($phi == 270) { $nextY += 4 }

        $c1->createLine( $thisX, $thisY, $nextX, $nextY,
                         -fill => 'white' );

        $mw->update;
      }
  }

$c1->createText( 350, 350,
                 -text => "P E R L  \n           M O N K S",
                 -fill => 'white',
                 -width => 300);

MainLoop;
[download]

__SIG__
printf "You are here %08x\n", unpack "L!", unpack "P4", pack
  "L!", B::svref_2object(sub{})->OUTSIDE;
[download]

You're right, diotalevi, it is a fractal. Good eyes! Specifically, it's a Lindenmayer system (L-system) type of fractal. A definition of this type of fractal is:

"A L-system or Lindenmayer system is a formal grammar for generating strings. (That is, it is a collection of rules such as replace X with XYX.) By recursively applying the rules of the L-system to an initial string, a string with fractal structure can be created. Interpreting this string as a set of graphical commands allows the fractal to be displayed. L-systems are very useful for generating realistic plant structures."

The above definition comes from this FAQ.

I just recently started reading about fractals, and since this type is string-based, I thought it would be fun to try it out with Perl. The starting shape that I used looked something like this (please excuse the ASCII art):

***  ***
  *  *
  ****

Hope this helps, and thanks for the comments.

So then snowflakes, themselves, are fractals? I always thought that fractals were designs that really had no symmetrical pattern like that, but more random patterns. Cool, I learned something. I like that. Word!
_____________________________________________________
mojobozo
word (wûrd)
interj. Slang. Used to express approval or an affirmative response to
something. Sometimes used with up. Source

Very nice indeed! But, to me, it looks more like a snowflake or tile than a fractal.
_____________________________________________________
mojobozo
word (wûrd)
interj. Slang. Used to express approval or an affirmative response to
something. Sometimes used with up. Source

Try playing with that for 1 .. 4 loop. I really don't know fractals so to my uneducated eye it looks like more detail after more iterations. I pushed it up to 5 but it didn't fit ony my screen anymore.

__SIG__
printf "You are here %08x\n", unpack "L!", unpack "P4", pack
  "L!", B::svref_2object(sub{})->OUTSIDE;
[download]

http://www.iit.edu/~fockjef/junk/lsys/