sclass RenderFrequencySample_SquareWave is RenderFrequencySample {
  public double get(Complex c, double frac) {
    double abs = c.abs();
    if (abs == 0) ret 0;
    frac = frac_nonNeg(frac + c.fracAngle());
    ret abs * (frac < .5 ? 1 : -1);
  }
  
  public void subtractPeriodFrom(AudioAdder audio, DoubleRange period, Complex intensity) {
    double goHigh = fracNonNeg(-intensity.fracAngle());
    double abs = intensity.abs();
    double goLow = fracNonNeg(goHigh+.5);
    double t1 = period.start, t2 = period.end, n = l(period);
    printVars(+t1, +t2, +goHigh, +goLow, +abs, +n);
    if (goHigh < goLow) {
      audio.subtractPlateau(t1, t1+goHigh*n,             -abs);
      audio.subtractPlateau(    t1+goHigh*n, t1+goLow*n,  abs);
      audio.subtractPlateau(    t1+goLow*n,  t2,         -abs);
    } else {
      audio.subtractPlateau(t1, t1+goLow*n,                abs);
      audio.subtractPlateau(    t1+goLow*n,  t1+goHigh*n, -abs);
      audio.subtractPlateau(    t1+goHigh*n, t2,           abs);
    }
  }
}