wolffd@0: load ('def.lefty');
wolffd@0: definit ();
wolffd@0: #
wolffd@0: # initialize window data
wolffd@0: #
wolffd@0: canvas = defcanvas;
wolffd@0: wrect = [0 = ['x' = 0; 'y' = 0;]; 1 = ['x' = 400; 'y' = 500;];];
wolffd@0: setwidgetattr (canvas, ['window' = wrect;]);
wolffd@0: 
wolffd@0: sq = function (x) {
wolffd@0:     return x * x;
wolffd@0: };
wolffd@0: 
wolffd@0: # data structures
wolffd@0: #
wolffd@0: length = 300;
wolffd@0: center = ['x' = 200; 'y' = 250;];
wolffd@0: radius = 2 * length / sqrt (12);
wolffd@0: fractalangle = 0;
wolffd@0: maxlevel = 2;
wolffd@0: 
wolffd@0: # drawing functions
wolffd@0: #
wolffd@0: # draw a Koch curve (a ``snowflake'' fractal)
wolffd@0: #
wolffd@0: # start with a triangle and keep replacing edges
wolffd@0: # with the construct: _/\_
wolffd@0: # until the recursion level reaches 'maxlevel'
wolffd@0: #
wolffd@0: fractal = function (level, length, angle) {
wolffd@0:     local nlength, newpenpos;
wolffd@0: 
wolffd@0:     if (level >= maxlevel) {
wolffd@0:         newpenpos.x = penpos.x + length * cos (angle);
wolffd@0:         newpenpos.y = penpos.y + length * sin (angle);
wolffd@0:         line (canvas, null, penpos, newpenpos, ['color' = 1;]);
wolffd@0:         penpos = newpenpos;
wolffd@0:         return;
wolffd@0:     }
wolffd@0:     nlength = length / 3;
wolffd@0:     fractal (level + 1, nlength, angle);
wolffd@0:     fractal (level + 1, nlength, angle + 60);
wolffd@0:     fractal (level + 1, nlength, angle - 60);
wolffd@0:     fractal (level + 1, nlength, angle);
wolffd@0: };
wolffd@0: drawfractal = function () {
wolffd@0:     clear (canvas);
wolffd@0:     setpick (canvas, center, wrect);
wolffd@0:     penpos = [
wolffd@0:         'x' = center.x + cos (fractalangle + 210) * radius;
wolffd@0:         'y' = center.y + sin (fractalangle + 210) * radius;
wolffd@0:     ];
wolffd@0:     fractal (0, length, fractalangle +  60);
wolffd@0:     fractal (0, length, fractalangle -  60);
wolffd@0:     fractal (0, length, fractalangle - 180);
wolffd@0:     remove ('penpos');
wolffd@0: };
wolffd@0: 
wolffd@0: # editing functions
wolffd@0: #
wolffd@0: # transform the fractal.
wolffd@0: #
wolffd@0: # map point 'prevpoint' to point 'currpoint'
wolffd@0: # with respect to the center of the fractal.
wolffd@0: #
wolffd@0: transformfractal = function (prevpoint, currpoint) {
wolffd@0:     local prevtan, currtan, prevradius, currradius;
wolffd@0: 
wolffd@0:     prevtan = atan (prevpoint.y - center.y, prevpoint.x - center.x);
wolffd@0:     currtan = atan (currpoint.y - center.y, currpoint.x - center.x);
wolffd@0:     fractalangle = fractalangle + (currtan - prevtan);
wolffd@0:     prevradius = sqrt (
wolffd@0:         sq (prevpoint.y - center.y) + sq (prevpoint.x - center.x)
wolffd@0:     );
wolffd@0:     currradius = sqrt (
wolffd@0:         sq (currpoint.y - center.y) + sq (currpoint.x - center.x)
wolffd@0:     );
wolffd@0:     radius = radius / prevradius * currradius;
wolffd@0:     length = radius / 2 * sqrt (12);
wolffd@0: };
wolffd@0: 
wolffd@0: # user interface functions
wolffd@0: #
wolffd@0: # bind changes to the fractal to user actions
wolffd@0: #
wolffd@0: leftup = function (data) {
wolffd@0:     transformfractal (data.ppos, data.pos);
wolffd@0:     drawfractal ();
wolffd@0: };
wolffd@0: dops = function () {
wolffd@0:     local s;
wolffd@0: 
wolffd@0:     s = ['x' = 8 * 300; 'y' = 10.5 * 300;];
wolffd@0:     canvas = createwidget (-1, ['type' = 'ps'; 'size' = s;]);
wolffd@0:     setwidgetattr (canvas, ['window' = wrect;]);
wolffd@0:     drawfractal ();
wolffd@0:     destroywidget (canvas);
wolffd@0:     canvas=defcanvas;
wolffd@0: };
wolffd@0: transformfractal (['x' = 0; 'y' = 0;], ['x' = 0; 'y' = 0;]);
wolffd@0: drawfractal ();