| 18 | static const char *transformer_2d = "wrot-2d"; |
| 19 | |
| 20 | static double cross(double x1, double y1, double x2, double y2) // cross product |
| 21 | { |
| 22 | return x1 * y2 - x2 * y1; |
| 23 | } |
| 24 | |
| 25 | static double vlen(double x1, double y1) // length of vector centered at the origin |
| 26 | { |