// -------------------------------------------------------
//   xplot.h   // global xplot for *fun
// -------------------------------------------------------
//   uses gwin and fun
// -----------------------
	void xplot(gwin w, fun *fu)
	 {
		double xa = w.getscale(1);
		double xb = w.getscale(2);
		int nn = w.getscan();
      if (nn <= 0) nn = 100;
      double x,dx,y;
      dx = (xb - xa)/nn;
		x = xa;
		y = fu->f(x);
		w.move(x,y);
      for (int j = 1; j <= nn; j++)
	    { x = xa + dx*j;
			y = fu->f(x);
			w.line(x,y); }
	 }
// --------------------------------------------------------