oscillators.cpp

#include <cmath>
#include <complex>

class Oscillator {
 private:
  double mRate;
  double mReal;
  double mImag;

 public:
  Oscillator(unsigned int rate)
      : mReal(0.0), mImag(1.0), mRate(static_cast<double>(rate)) {}
  double next(double freq);
};

double Oscillator::next(double freq) {
  const double tau = 6.28318530717958623199592693709;
  double a = tau * freq / mRate;
  double u = cos(a);
  double v = sin(a);
  double x = mReal * u - mImag * v;
  double y = mReal * v + mImag * u;
  mReal = x;
  mImag = y;
  return mReal;
}

class Oscillator2 {
 private:
  double mRate;
  double mPhase;

 public:
  Oscillator2(unsigned int rate)
      : mPhase(0.0), mRate(static_cast<double>(rate)) {}
  double next(double freq);
};

double Oscillator2::next(double freq) {
  const double tau = 6.28318530717958623199592693709;
  mPhase += tau * freq / mRate;
  if (mPhase > tau) {
    mPhase -= tau;
  }
  return sin(mPhase);
}

class Oscillator3 {
 private:
  double mRate;
  std::complex<double> mValue;

 public:
  Oscillator3(unsigned int rate)
      : mValue(0.0), mRate(static_cast<double>(rate)) {}
  double next(double freq);
};

double Oscillator3::next(double freq) {
  const double tau = 6.28318530717958623199592693709;
  mValue *= std::exp(std::complex<double>(0.0f, tau * freq / mRate));
  return mValue.real();
}