float->float pipeline BandPassFilter (float rate, float low, float high, int taps) {
  add BPFCore(rate, low, high, taps);
  add Subtracter();
}
float->float splitjoin BPFCore (float rate, float low, float high, int taps) {
  split duplicate;
  add LowPassFilter(rate, low, taps, 0);
  add LowPassFilter(rate, high, taps, 0);
  join roundrobin;
}
float->float filter Subtracter {
  work pop 2 push 1 {
    push(peek(1) - peek(0));
    pop(); pop();
  }
}

float->float filter LowPassFilter(float rate, float cutoff, 
                                  int taps, int decimation) {
  float[taps] coeff;
  init {
    int i;
    float m = taps - 1;
    float w = 2 * pi * cutoff / rate;
    for (i = 0; i < taps; i++) {
      if (i - m/2 == 0)
        coeff[i] = w/pi;
      else
        coeff[i] = sin(w*(i-m/2)) / pi / (i-m/2) *
          (0.54 - 0.46 * cos(2*pi*i/m));
    }
  }
  work pop 1+decimation push 1 peek taps {
    float sum = 0;
    for (int i = 0; i < taps; i++)
      sum += peek(i) * coeff[i];
    push(sum);
    for (int i=0; i<decimation; i++)
      pop();
    pop();
  }
}

void->void pipeline BPFProgram {
  add FloatSource();
  add BandPassFilter(250000000, 1000, 1200, 64);
  add FloatPrinter();
}

void->float filter FloatSource {
  float x;
  init { x = 0; }
  work push 1 {
    push(x);
    x = x + 1.0;
  }
}

float->void filter FloatPrinter {
  work pop 1 { println(pop()); }
}