/* boost random/xor_combine.hpp header file

 *

 * Copyright Jens Maurer 2002

 * Distributed under the Boost Software License, Version 1.0. (See

 * accompanying file LICENSE_1_0.txt or copy at

 * http://www.boost.org/LICENSE_1_0.txt)

 *

 * See http://www.boost.org for most recent version including documentation.

 *

 * $Id: xor_combine.hpp,v 1.13 2005/05/21 15:57:00 dgregor Exp $

 *

 */

#ifndef BOOST_RANDOM_XOR_COMBINE_HPP

#define BOOST_RANDOM_XOR_COMBINE_HPP

#include <iostream>

#include <cassert>

#include <algorithm> // for std::min and std::max

#include <boost/config.hpp>

#include <boost/limits.hpp>

#include <boost/static_assert.hpp>

#include <boost/cstdint.hpp>     // uint32_t

namespace boost {

namespace random {

template<class URNG1, int s1, class URNG2, int s2,

#ifndef BOOST_NO_DEPENDENT_TYPES_IN_TEMPLATE_VALUE_PARAMETERS

  typename URNG1::result_type 

#else

  uint32_t

#endif

  val = 0>

class xor_combine

{

public:

  typedef URNG1 base1_type;

  typedef URNG2 base2_type;

  typedef typename base1_type::result_type result_type;

  BOOST_STATIC_CONSTANT(bool, has_fixed_range = false);

  BOOST_STATIC_CONSTANT(int, shift1 = s1);

  BOOST_STATIC_CONSTANT(int, shfit2 = s2);

  xor_combine() : _rng1(), _rng2()

  { }

  xor_combine(const base1_type & rng1, const base2_type & rng2)

    : _rng1(rng1), _rng2(rng2) { }

  template<class It> xor_combine(It& first, It last)

    : _rng1(first, last), _rng2( /* advanced by other call */ first, last) { }

  void seed() { _rng1.seed(); _rng2.seed(); }

  template<class It> void seed(It& first, It last)

  {

    _rng1.seed(first, last);

    _rng2.seed(first, last);

  }

  const base1_type& base1() { return _rng1; }

  const base2_type& base2() { return _rng2; }

  result_type operator()()

  {

    // MSVC fails BOOST_STATIC_ASSERT with std::numeric_limits at class scope

#if !defined(BOOST_NO_LIMITS_COMPILE_TIME_CONSTANTS) && !(defined(BOOST_MSVC) && BOOST_MSVC <= 1300)

    BOOST_STATIC_ASSERT(std::numeric_limits<typename base1_type::result_type>::is_integer);

    BOOST_STATIC_ASSERT(std::numeric_limits<typename base2_type::result_type>::is_integer);

    BOOST_STATIC_ASSERT(std::numeric_limits<typename base1_type::result_type>::digits >= std::numeric_limits<typename base2_type::result_type>::digits);

#endif

    return (_rng1() << s1) ^ (_rng2() << s2);

  }

  result_type min BOOST_PREVENT_MACRO_SUBSTITUTION () const { return std::min BOOST_PREVENT_MACRO_SUBSTITUTION((_rng1.min)(), (_rng2.min)()); }

  result_type max BOOST_PREVENT_MACRO_SUBSTITUTION () const { return std::max BOOST_PREVENT_MACRO_SUBSTITUTION((_rng1.min)(), (_rng2.max)()); }

  static bool validation(result_type x) { return val == x; }

#ifndef BOOST_NO_OPERATORS_IN_NAMESPACE

#ifndef BOOST_NO_MEMBER_TEMPLATE_FRIENDS

  template<class CharT, class Traits>

  friend std::basic_ostream<CharT,Traits>&

  operator<<(std::basic_ostream<CharT,Traits>& os, const xor_combine& s)

  {

    os << s._rng1 << " " << s._rng2 << " ";

    return os;

  }

  template<class CharT, class Traits>

  friend std::basic_istream<CharT,Traits>&

  operator>>(std::basic_istream<CharT,Traits>& is, xor_combine& s)

  {

    is >> s._rng1 >> std::ws >> s._rng2 >> std::ws;

    return is;

  }

#endif

  friend bool operator==(const xor_combine& x, const xor_combine& y)

  { return x._rng1 == y._rng1 && x._rng2 == y._rng2; }

  friend bool operator!=(const xor_combine& x, const xor_combine& y)

  { return !(x == y); }

#else

  // Use a member function; Streamable concept not supported.

  bool operator==(const xor_combine& rhs) const

  { return _rng1 == rhs._rng1 && _rng2 == rhs._rng2; }

  bool operator!=(const xor_combine& rhs) const

  { return !(*this == rhs); }

#endif

private:

  base1_type _rng1;

  base2_type _rng2;

};

#ifndef BOOST_NO_INCLASS_MEMBER_INITIALIZATION

//  A definition is required even for integral static constants

template<class URNG1, int s1, class URNG2, int s2,

#ifndef BOOST_NO_DEPENDENT_TYPES_IN_TEMPLATE_VALUE_PARAMETERS

  typename URNG1::result_type 

#else

  uint32_t

#endif

  val>

const bool xor_combine<URNG1, s1, URNG2, s2, val>::has_fixed_range;

#endif

} // namespace random

} // namespace boost

#endif // BOOST_RANDOM_XOR_COMBINE_HPP