Material.hpp

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// This file is part of the Acts project.
//
// Copyright (C) 2016-2020 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/.

#pragma once

#include "Acts/Definitions/Algebra.hpp"

#include <iosfwd>
#include <limits>
#include <utility>

namespace Acts {

class Material {
 public:
  using ParametersVector = Eigen::Matrix<float, 5, 1>;

  // Both mass and molar density are stored as a float and can thus not be
  // distinguished by their types. Just changing the last element in the
  // previously existing constructor that took five floats as input to represent
  // molar density instead of mass density could have lead to significant
  // confusion compared to the previous behaviour. To avoid any ambiguity,
  // construction from separate material parameters must happen through the
  // following named constructors.

  static Material fromMolarDensity(float x0, float l0, float ar, float z,
                                   float molarRho);
  static Material fromMassDensity(float x0, float l0, float ar, float z,
                                  float massRho);
  Material() = default;
  Material(const ParametersVector& parameters);

  Material(Material&& mat) = default;
  Material(const Material& mat) = default;
  ~Material() = default;
  Material& operator=(Material&& mat) = default;
  Material& operator=(const Material& mat) = default;

  constexpr operator bool() const { return 0.0f < m_ar; }

  constexpr float X0() const { return m_x0; }
  constexpr float L0() const { return m_l0; }
  constexpr float Ar() const { return m_ar; }
  constexpr float Z() const { return m_z; }
  constexpr float molarDensity() const { return m_molarRho; }
  constexpr float molarElectronDensity() const { return m_z * m_molarRho; }
  float massDensity() const;
  float meanExcitationEnergy() const;

  ParametersVector parameters() const;

 private:
  float m_x0 = std::numeric_limits<float>::infinity();
  float m_l0 = std::numeric_limits<float>::infinity();
  float m_ar = 0.0f;
  float m_z = 0.0f;
  float m_molarRho = 0.0f;

  friend constexpr bool operator==(const Material& lhs, const Material& rhs) {
    return (lhs.m_x0 == rhs.m_x0) and (lhs.m_l0 == rhs.m_l0) and
           (lhs.m_ar == rhs.m_ar) and (lhs.m_z == rhs.m_z) and
           (lhs.m_molarRho == rhs.m_molarRho);
  }
  friend constexpr bool operator!=(const Material& lhs, const Material& rhs) {
    return !(lhs == rhs);
  }
};

std::ostream& operator<<(std::ostream& os, const Material& material);

}  // namespace Acts