#ifndef _MATH_H#include <math.h>#endif#include "fdtd3.h"#include "ezinc.h"static int tfsfBoundary=0;  void tfsfInit(Grid *g) {      printf("Enter location of TFSF boundary: ");  scanf(" %d",&tfsfBoundary);  ezIncInit(g); // initialize source function   return;}void tfsfUpdate(Grid *g) {     /* check if tfsfInit() has been called */  if (tfsfBoundary<=0) {    fprintf(stderr,      "tfsfUpdate: tfsfInit must be called before tfsfUpdate.\n"      "            Boundary location must be set to positive value.\n");    exit(-1);  }  /* correct Hy adjacent to TFSF boundary */  Hy(tfsfBoundary) -= ezInc(Time,0.0)*Chye(tfsfBoundary);      /* correct Ez adjacent to TFSF boundary */  Ez(tfsfBoundary+1) += ezInc(Time+0.5,-0.5);    return;}