/* boost random/discard_block.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: discard_block.hpp,v 1.12 2005/05/21 15:57:00 dgregor Exp $

 *

 * Revision history

 *  2001-03-02  created

 */

#ifndef BOOST_RANDOM_DISCARD_BLOCK_HPP

#define BOOST_RANDOM_DISCARD_BLOCK_HPP

#include <iostream>

#include <boost/config.hpp>

#include <boost/limits.hpp>

#include <boost/static_assert.hpp>

namespace boost {

namespace random {

template<class UniformRandomNumberGenerator, unsigned int p, unsigned int r>

class discard_block

{

public:

  typedef UniformRandomNumberGenerator base_type;

  typedef typename base_type::result_type result_type;

  BOOST_STATIC_CONSTANT(bool, has_fixed_range = false);

  BOOST_STATIC_CONSTANT(unsigned int, total_block = p);

  BOOST_STATIC_CONSTANT(unsigned int, returned_block = r);

#ifndef BOOST_NO_LIMITS_COMPILE_TIME_CONSTANTS

  BOOST_STATIC_ASSERT(total_block >= returned_block);

#endif

  discard_block() : _rng(), _n(0) { }

  explicit discard_block(const base_type & rng) : _rng(rng), _n(0) { }

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

    : _rng(first, last), _n(0) { }

  void seed() { _rng.seed(); _n = 0; }

  template<class T> void seed(T s) { _rng.seed(s); _n = 0; }

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

  { _n = 0; _rng.seed(first, last); }

  const base_type& base() const { return _rng; }

  result_type operator()()

  {

    if(_n >= returned_block) {

      // discard values of random number generator

      for( ; _n < total_block; ++_n)

        _rng();

      _n = 0;

    }

    ++_n;

    return _rng();

  }

  result_type min BOOST_PREVENT_MACRO_SUBSTITUTION () const { return (_rng.min)(); }

  result_type max BOOST_PREVENT_MACRO_SUBSTITUTION () const { return (_rng.max)(); }

  static bool validation(result_type x) { return true; }  // dummy

#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 discard_block& s)

  {

    os << s._rng << " " << s._n << " ";

    return os;

  }

  template<class CharT, class Traits>

  friend std::basic_istream<CharT,Traits>&

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

  {

    is >> s._rng >> std::ws >> s._n >> std::ws;

    return is;

  }

#endif

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

  { return x._rng == y._rng && x._n == y._n; }

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

  { return !(x == y); }

#else

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

  bool operator==(const discard_block& rhs) const

  { return _rng == rhs._rng && _n == rhs._n; }

  bool operator!=(const discard_block& rhs) const

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

#endif

private:

  base_type _rng;

  unsigned int _n;

};

#ifndef BOOST_NO_INCLASS_MEMBER_INITIALIZATION

//  A definition is required even for integral static constants

template<class UniformRandomNumberGenerator, unsigned int p, unsigned int r>

const bool discard_block<UniformRandomNumberGenerator, p, r>::has_fixed_range;

template<class UniformRandomNumberGenerator, unsigned int p, unsigned int r>

const unsigned int discard_block<UniformRandomNumberGenerator, p, r>::total_block;

template<class UniformRandomNumberGenerator, unsigned int p, unsigned int r>

const unsigned int discard_block<UniformRandomNumberGenerator, p, r>::returned_block;

#endif

} // namespace random

} // namespace boost

#endif // BOOST_RANDOM_DISCARD_BLOCK_HPP