void fz(double complex *z){// The function values 
    int n;
//    double Pi=acos(-1.0L);
    for(n=0;n<N;n++){
	double u = 2.0*Pi*(double)n/(double)N;
//	z[n] = 1.0;
//	z[n] = sin(u); //OK with equidistant!
//	z[n] = cos(u); //OK with equidistant!
	z[n] = exp(-sqr(u-Pi)/(2.0*0.16)); // Gibbs Oscillations near endpoints as expected 



    }
}