ceph/src/civetweb/src/third_party/duktape-1.5.2/mandel.js

   1 /*
   2  *  Mandelbrot example:
   3  *
   4  *    $ ./duk mandel.js
   5  *    [...]
   6  */
   7
   8 function mandel() {
   9     var w = 76, h = 28, iter = 100;
  10     var i, j, k, c;
  11     var x0, y0, xx, yy, xx2, yy2;
  12     var line;
  13
  14     for (i = 0; i < h; i++) {
  15         y0 = (i / h) * 2.5 - 1.25;
  16
  17         for (j = 0, line = []; j < w; j++) {
  18             x0 = (j / w) * 3.0 - 2.0;
  19
  20             for (k = 0, xx = 0, yy = 0, c = '#'; k < iter; k++) {
  21                 /* z -> z^2 + c
  22                  *   -> (xx+i*yy)^2 + (x0+i*y0)
  23                  *   -> xx*xx+i*2*xx*yy-yy*yy + x0 + i*y0
  24                  *   -> (xx*xx - yy*yy + x0) + i*(2*xx*yy + y0)
  25                  */
  26
  27                 xx2 = xx*xx; yy2 = yy*yy;
  28
  29                 if (xx2 + yy2 < 4.0) {
  30                     yy = 2*xx*yy + y0;
  31                     xx = xx2 - yy2 + x0;
  32                 } else {
  33                     /* xx^2 + yy^2 >= 4.0 */
  34                     if (k < 3) { c = '.'; }
  35                     else if (k < 5) { c = ','; }
  36                     else if (k < 10) { c = '-'; }
  37                     else { c = '='; }
  38                     break;
  39                 }
  40             }
  41
  42             line.push(c);
  43         }
  44
  45         print(line.join(''));
  46     }
  47 }
  48
  49 try {
  50     mandel();
  51 } catch (e) {
  52     print(e.stack || e);
  53 }