/* Commandline execution:
 * 		civl verify diffusion.cvl
 */
int nx;
$input double u0[2];
int nsteps;
double kappa;
double data[3][2];
double u[2];

void init() {  
  nx = 2;
  nsteps = 2;
  kappa = 0.1;
  for (int i = 0; i < nx; i++) {
    u[i] = u0[i];
  }
}

void write(int time) {
  for (int i = 0; i < nx; i++) {
    data[time][i] = u[i];
  }
}

void update() {
	double u_new[nx];
	
	for (int i=1; i<nx-1; i++) {
	  u_new[i] =  u[i] + kappa*(u[i+1] + u[i-1] - 2*u[i]);
    }
	for (int i=1; i<nx-1; i++) {
	  u[i] = u_new[i];
	}
}

void main() {
	init();
	write(0);
	for (int iter = 1; iter <= nsteps; iter++) {
		update();
		write(iter);
	}
}