sclass AudioSampleOps {
  // implementation of gain modifier
  srecord noeq Gain(double factor, IAudioSample original) implements IAudioSample {
    public double sampleRate() { ret original.sampleRate(); }
    public int channels() { ret original.channels(); }
    public DoubleRange bounds() { ret original.bounds(); }
    
    public double sampleSum(int channel, double start, double end) {
      ret original.sampleSum(channel, start, end)*factor;
    }
    
    // coalesce consecutive gains
    public IAudioSample gain(double factor) {
      ret original.gain(this.factor*factor);
    }
  }
  
  // Implementation of the time-shift modifier.
  // moves the input <shift> samples to the left (cuts off beginning).
  // Shift can be fractional - we're in integral image (audio) wonderland after all
  // where a traditional pixel has no meaning.
  srecord noeq TimeShift(double shift, IAudioSample original) implements IAudioSample {
    public double sampleRate() { ret original.sampleRate(); }
    public int channels() { ret original.channels(); }
    public DoubleRange bounds() { ret shiftDoubleRange(original.bounds(), -shift); }

    public double sampleSum(int channel, double start, double end) {
      ret original.sampleSum(channel, start+shift, end+shift);
    }
    
    // coalesce consecutive time-shifts
    public IAudioSample timeShift(double shift) {
      ret original.timeShift(this.shift+shift);
    }
  }
  
  // Implementation of the speed-up modifier which transforms every frequency f to f*factor.
  // This is for convenience, you could also just call sampleSum() directly with larger intervals.
  sclass SpeedUp implements IAudioSample {
    double factor, invFactor;
    IAudioSample original;

    *(double *factor, IAudioSample *original) {
      if (factor < 1) fail("Can't slow down. " + factor);
      invFactor = 1/factor;
    }
    
    public double sampleRate() { ret original.sampleRate()*invFactor; }
    public int channels() { ret original.channels(); }
    public DoubleRange bounds() { ret scaleDoubleRange(original.bounds(), invFactor); }
    
    public double sampleSum(int channel, double start, double end) {
      ret original.sampleSum(channel, start*factor, end*factor)*invFactor;
    }
    
    // coalesce consecutive speed-ups
    public IAudioSample speedUp(double factor) {
      ret original.speedUp(this.factor*factor);
    }
  }
}