/* boost random/additive_combine.hpp header file
 *
 * Copyright Jens Maurer 2000-2001
 * Permission to use, copy, modify, sell, and distribute this software
 * is hereby granted without fee provided that the above copyright notice
 * appears in all copies and that both that copyright notice and this
 * permission notice appear in supporting documentation,
 *
 * Jens Maurer makes no representations about the suitability of this
 * software for any purpose. It is provided "as is" without express or
 * implied warranty.
 *
 * See http://www.boost.org for most recent version including documentation.
 *
 * $Id: additive_combine.hpp,v 1.3 2001/06/01 17:11:49 jmaurer Exp $
 *
 * Revision history
 *  2001-02-18  moved to individual header files
 */

#ifndef BOOST_RANDOM_ADDITIVE_COMBINE_HPP
#define BOOST_RANDOM_ADDITIVE_COMBINE_HPP

#include <iostream>
#include <boost/config.hpp>
#include <boost/cstdint.hpp>
#include <boost/random/linear_congruential.hpp>

namespace boost {
namespace random {

// L'Ecuyer 1988
template<class MLCG1, class MLCG2,
#ifndef BOOST_NO_DEPENDENT_TYPES_IN_TEMPLATE_VALUE_PARAMETERS
  typename MLCG1::result_type 
#else
  int32_t
#endif
  val>
class additive_combine
{
public:
  typedef MLCG1 first_base;
  typedef MLCG2 second_base;
  typedef typename MLCG1::result_type result_type;
#ifndef BOOST_NO_INCLASS_MEMBER_INITIALIZATION
  static const bool has_fixed_range = true;
  static const result_type min_value = 1;
  static const result_type max_value = MLCG1::max_value-1;
#else
  enum { has_fixed_range = false };
#endif
  result_type min() const { return 1; }
  result_type max() const { return _mlcg1.max()-1; }

  additive_combine() : _mlcg1(), _mlcg2() { }
  additive_combine(typename MLCG1::result_type seed1, 
                   typename MLCG2::result_type seed2)
    : _mlcg1(seed1), _mlcg2(seed2) { }
  result_type operator()() {
    result_type z = _mlcg1() - _mlcg2();
    if(z < 1)
      z += MLCG1::modulus-1;
    return z;
  }
  bool validation(result_type x) const { return val == x; }

#ifndef BOOST_NO_OPERATORS_IN_NAMESPACE
  friend std::ostream& operator<<(std::ostream& os, const additive_combine& r)
  { os << r._mlcg1 << " " << r._mlcg2; return os; }
  friend std::istream& operator>>(std::istream& is, additive_combine& r)
  { is >> r._mlcg1 >> std::ws >> r._mlcg2; return is; }
  friend bool operator==(const additive_combine& x, const additive_combine& y)
  { return x._mlcg1 == y._mlcg1 && x._mlcg2 == y._mlcg2; }
#else
  // Use a member function; Streamable concept not supported.
  bool operator==(const additive_combine& rhs) const
  { return _mlcg1 == rhs._mlcg1 && _mlcg2 == rhs._mlcg2; }
#endif
private:
  MLCG1 _mlcg1;
  MLCG2 _mlcg2;
};

} // namespace random

typedef random::additive_combine<
    random::linear_congruential<int32_t, 40014, 0, 2147483563, 0>,
    random::linear_congruential<int32_t, 40692, 0, 2147483399, 0>,
  2060321752> ecuyer1988;

} // namespace boost

#endif // BOOST_RANDOM_ADDITIVE_COMBINE_HPP
