#include <stdio.h>
#include <math.h>

main() {

  int N;
  int M=1000;
  float fs=8000.0;
  FILE* fp=fopen("fresp.dat", "w");

  fprintf(stdout, "enter order:\n");
  fscanf(stdin, "%d", &N);

  float *x = new float[N];

  for (int i=0; i<N; i++) {
    fprintf(stdout, "enter coeff #%d\n", i);
    fscanf(stdin, "%f", &x[i]);
  }

  printf("\norder = %d\n", N);
  for (i=0; i<N; i++) {
    fprintf(stdout, "h[%2d] = %f\n", i, x[i]);
  }

  // do the DFT
  //

  for (int k=0; k<(M/2); k++) {
    float f = (float)k/(float)M;
    float sumr=0, sumi=0, sum=0;
    for (int n=0; n<N; n++) {
      sumr += x[n] * cos(2.0*M_PI*f*n);
      sumi -= x[n] * sin(2.0*M_PI*f*n);
    }
    sum = sumr*sumr + sumi*sumi;
    if (sum == 0)
      {sum = -100.0;}
    else
      {sum = 10.0 * log10(sum);}
    fprintf(fp, "%f %f\n", fs/2.0/M*k, sum);
  }

  fclose(fp);

}