/* boost random/inversive_congruential.hpp header file

 *

 * Copyright Jens Maurer 2000-2001

 * 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: inversive_congruential.hpp,v 1.11 2005/05/21 15:57:00 dgregor Exp $

 *

 * Revision history

 *  2001-02-18  moved to individual header files

 */

#ifndef BOOST_RANDOM_INVERSIVE_CONGRUENTIAL_HPP

#define BOOST_RANDOM_INVERSIVE_CONGRUENTIAL_HPP

#include <iostream>

#include <cassert>

#include <boost/config.hpp>

#include <boost/static_assert.hpp>

#include <boost/random/detail/const_mod.hpp>

namespace boost {

namespace random {

// Eichenauer and Lehn 1986

template<class IntType, IntType a, IntType b, IntType p, IntType val>

class inversive_congruential

{

public:

  typedef IntType result_type;

#ifndef BOOST_NO_INCLASS_MEMBER_INITIALIZATION

  static const bool has_fixed_range = true;

  static const result_type min_value = (b == 0 ? 1 : 0);

  static const result_type max_value = p-1;

#else

  BOOST_STATIC_CONSTANT(bool, has_fixed_range = false);

#endif

  BOOST_STATIC_CONSTANT(result_type, multiplier = a);

  BOOST_STATIC_CONSTANT(result_type, increment = b);

  BOOST_STATIC_CONSTANT(result_type, modulus = p);

  result_type min BOOST_PREVENT_MACRO_SUBSTITUTION () const { return b == 0 ? 1 : 0; }

  result_type max BOOST_PREVENT_MACRO_SUBSTITUTION () const { return p-1; }

  explicit inversive_congruential(IntType y0 = 1) : value(y0)

  {

    BOOST_STATIC_ASSERT(b >= 0);

    BOOST_STATIC_ASSERT(p > 1);

    BOOST_STATIC_ASSERT(a >= 1);

    if(b == 0) 

      assert(y0 > 0); 

  }

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

  { seed(first, last); }

  void seed(IntType y0 = 1) { value = y0; if(b == 0) assert(y0 > 0); }

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

  {

    if(first == last)

      throw std::invalid_argument("inversive_congruential::seed");

    value = *first++;

  }

  IntType operator()()

  {

    typedef const_mod<IntType, p> do_mod;

    value = do_mod::mult_add(a, do_mod::invert(value), b);

    return value;

  }

  bool validation(result_type x) const { 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, inversive_congruential x)

  { os << x.value; return os; }

  template<class CharT, class Traits>

  friend std::basic_istream<CharT,Traits>&

  operator>>(std::basic_istream<CharT,Traits>& is, inversive_congruential& x)

  { is >> x.value; return is; }

#endif

  friend bool operator==(inversive_congruential x, inversive_congruential y)

  { return x.value == y.value; }

  friend bool operator!=(inversive_congruential x, inversive_congruential y)

  { return !(x == y); }

#else

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

  bool operator==(inversive_congruential rhs) const

  { return value == rhs.value; }

  bool operator!=(inversive_congruential rhs) const

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

#endif

private:

  IntType value;

};

#ifndef BOOST_NO_INCLASS_MEMBER_INITIALIZATION

//  A definition is required even for integral static constants

template<class IntType, IntType a, IntType b, IntType p, IntType val>

const bool inversive_congruential<IntType, a, b, p, val>::has_fixed_range;

template<class IntType, IntType a, IntType b, IntType p, IntType val>

const typename inversive_congruential<IntType, a, b, p, val>::result_type inversive_congruential<IntType, a, b, p, val>::min_value;

template<class IntType, IntType a, IntType b, IntType p, IntType val>

const typename inversive_congruential<IntType, a, b, p, val>::result_type inversive_congruential<IntType, a, b, p, val>::max_value;

template<class IntType, IntType a, IntType b, IntType p, IntType val>

const typename inversive_congruential<IntType, a, b, p, val>::result_type inversive_congruential<IntType, a, b, p, val>::multiplier;

template<class IntType, IntType a, IntType b, IntType p, IntType val>

const typename inversive_congruential<IntType, a, b, p, val>::result_type inversive_congruential<IntType, a, b, p, val>::increment;

template<class IntType, IntType a, IntType b, IntType p, IntType val>

const typename inversive_congruential<IntType, a, b, p, val>::result_type inversive_congruential<IntType, a, b, p, val>::modulus;

#endif

} // namespace random

typedef random::inversive_congruential<int32_t, 9102, 2147483647-36884165,

  2147483647, 0> hellekalek1995;

} // namespace boost

#endif // BOOST_RANDOM_INVERSIVE_CONGRUENTIAL_HPP