#ifndef  MIXTURE_HPP
#define  MIXTURE_HPP
// Created: 27-OCT-1998   Stephen Kahn
//
// $Revision: 1.2 $
//
// This code describes a mixture of materials in a manner similar to
// Geant 3.21.  This inherits from the Material class which describes
// the effective material description.  This class contains the relative
// weights of each material element and stores a vector containing the
// element materials.
//

// Include files

#include  <material/Material.hpp>
#include  <vector>

namespace  D0Material  {

  /** The D0 Mixture Class.
      
      This class is used to represent composite material as needed by the D0
      reconstruction program.
      
  */


class  Mixture: public Material {

public:

  /** Constructor calculates effective Material class parameters
      from weights of elements in composite material.  The procudure
      is that used in GEANT 3.21.
  */
  Mixture( const std::string& name, const std::string& symbol,
	   const std::vector<Material> elements, 
	   const std::vector<double> weights,
	   const bool weights_are_fractions=true);

  /// Deprecated intermediate constructor
  Mixture( const std::string& name, const std::string& symbol);

  /// Default constructor.  Needed for STL use
  Mixture() {}

  ///  Returns a vector of materials used to build this mixture
  std::vector<Material> get_materials() const  {  return _elements; }

  ///  Returns vector of material weights
  std::vector<double>    get_weights()  const   {  return _weights; }

  ///  Returns ith material
  Material  get_material(int i) const   {   return  _elements[i]; }

  ///  Returns ith material atomic fraction
  double   atomic_fraction(int i) const;

  ///  Returns ith material weight fraction
  double   weight_fraction( int i) const;

  ///  Returns weight type
  bool   weight_type() const  {  return _wtype; }

  ///  Returns number of elements
  int   numb_elements() const {  return _nlmat; }

  /// Add a new part to the composite, specifying its weight
  void  add_material_by_weight( const double, const Material& );

  /// Add a new part of the composite, specificying the fraction of the total
  void  add_material_by_fraction(const double, const Material&);

  /// Compute the properties of the composite
  void  calc_eff_material();

  /// Stream insertion
  friend  std::ostream& operator <<(std::ostream& os, const Mixture& me);
		
private:

  /// Fraction of total of each material in the composite
  std::vector<double>        _weights;  // atomic fractions

  /// List of materials which form the composite
  std::vector<Material>	_elements;     // Material of each element

  int  _nlmat;                         //  number of materials in Mixture

  ///  total weight -- used internally for normalization
  double _wtot;

  /// Flag indicating if weight are by number fraction(false) or weight fraction
  bool	_wtype;

};   // end class

std::ostream& operator <<(std::ostream& os, const Mixture& me);

}    // end namespace
#endif   // MIXTURE_HPP