#ifndef BIQUAD__H
#define BIQUAD__H
#include <complex>
#include <vector>

// typical usage:
// biquad butterworth({1., 2., 1.},
//         {1., -1.99911142347079540116, 0.99911181807963833634});

typedef std::complex<double> C;

class biquad{
public:
// d0 must always be 1
  std::vector<double> c, d;
  std::vector<C> zeros, poles;
  double ws1, ws2;      // remembered weighted sums

  C static constexpr C0 = C(0, 0);
  C static constexpr C1 = C(1, 0);
// gory-detail constructor
biquad(std::vector<double> const _c, std::vector<double> const _d,
                std::vector<C> _zeros, std::vector<C> _poles);

// constructor in terms of coefficients:
biquad(std::vector<double> const _c, std::vector<double> const _d);

// constructor in terms of zero and pole position,
// assuming conjugate pairs:
  biquad(C const zero, C const pole);

// time-domain evaluation:
  double step(double const Vin);

// z-plane transfer function
  C xfunc(const C z) const;

  void normalize(C const z = 1);
  void please_normalize(C const z = 1);
};

#endif