closed.h

#pragma once
#include <Eigen/Eigen>
#include <complex>

/* Solves the quadratic equation a*x^2 + b*x + c = 0 */
void solve_quadratic(double a, double b, double c, std::complex<double> roots[2]);

/* Solves the quadratic equation a*x^2 + b*x + c = 0 */
void solve_quadratic_old(double a, double b, double c, std::complex<double> roots[2]);

/* Solves the quartic equation p[2]*x^2 + p[1]*x + p[0] = 0 */
void solve_quadratic(double *p, std::complex<double> roots[4]);
/* Solves the cubic equation a*x^3 + b*x^2 + c*x + d = 0 */
void solve_cubic(double a, double b, double c, double d, std::complex<double> roots[3]);

/* Sign of component with largest magnitude */
double sign2(std::complex<double> z);

/* Solves the quartic equation x^4 + b*x^3 + c*x^2 + d*x + e = 0 */
void solve_quartic(double b, double c, double d, double e, std::complex<double> roots[4]);
/* Solves the quartic equation a*x^4 + b*x^3 + c*x^2 + d*x + e = 0 */
void solve_quartic(double a, double b, double c, double d, double e, std::complex<double> roots[4]);
/* Solves the quartic equation p[4]*x^4 + p[3]*x^3 + p[2]*x^2 + p[1]*x + p[0] = 0 */
void solve_quartic(double *p, std::complex<double> roots[4]);