Function duffing

Main.cpp:96–101

  y = ny;
}
void duffing(double& x, double& y, double cx, double cy) {
  double nx = y;
  double ny = -cy*x + cx*y - y*y*y;
  x = nx;
  y = ny;
}
void ikeda(double& x, double& y, double cx, double cy) {
  double t = 0.4 - 6.0 / (1.0 + x*x + y*y);
  double st = std::sin(t);