this is a gcc file, you can download it and learn its usetility, for further detail please look at t

				f(x, d1, d2, d3)				   double d1, d2, d3;				{				   return x;				}								g(b,s,x,y,i,j)				     char *b,*s;				     double x,y;				{				  if (x != 1.0 || y != 2.0 || i != 3 || j != 4)				    abort();				}								main()				{				  g("","", 1.0, 2.0, f(3, 0.0, 0.0, 0.0), f(4, 0.0, 0.0, 0.0));				  exit(0);				}