RealQuadraticEquation.hpp

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// This file is part of the Acts project.
//
// Copyright (C) 2017-2018 CERN for the benefit of the Acts project
//
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at http://mozilla.org/MPL/2.0/.

// RealQuadraticEquation.h, Acts project

#pragma once
#include <cmath>
#include <utility>

namespace Acts {
namespace detail {


struct RealQuadraticEquation {
  double first;
  double second;
  int solutions;

  RealQuadraticEquation(double alpha, double beta, double gamma)
      : first(0.), second(0.) {
    double discriminant = beta * beta - 4 * alpha * gamma;
    if (discriminant < 0) {
      solutions = 0;
    } else {
      solutions = (discriminant == 0) ? 1 : 2;
      double q = -0.5 * (beta + (beta > 0 ? std::sqrt(discriminant)
                                          : -std::sqrt(discriminant)));
      first = q / alpha;
      second = gamma / q;
    }
  }
};

}  // namespace detail
}  // namespace Acts