1 /* boost random/discard_block.hpp header file

     2  *

     3  * Copyright Jens Maurer 2002

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

     5  * accompanying file LICENSE_1_0.txt or copy at

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

     7  *

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

     9  *

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

    11  *

    12  * Revision history

    13  *  2001-03-02  created

    14  */

    15 

    16 #ifndef BOOST_RANDOM_DISCARD_BLOCK_HPP

    17 #define BOOST_RANDOM_DISCARD_BLOCK_HPP

    18 

    19 #include <iostream>

    20 #include <boost/config.hpp>

    21 #include <boost/limits.hpp>

    22 #include <boost/static_assert.hpp>

    23 

    24 

    25 namespace boost {

    26 namespace random {

    27 

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

    29 class discard_block

    30 {

    31 public:

    32   typedef UniformRandomNumberGenerator base_type;

    33   typedef typename base_type::result_type result_type;

    34 

    35   BOOST_STATIC_CONSTANT(bool, has_fixed_range = false);

    36   BOOST_STATIC_CONSTANT(unsigned int, total_block = p);

    37   BOOST_STATIC_CONSTANT(unsigned int, returned_block = r);

    38 

    39 #ifndef BOOST_NO_LIMITS_COMPILE_TIME_CONSTANTS

    40   BOOST_STATIC_ASSERT(total_block >= returned_block);

    41 #endif

    42 

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

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

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

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

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

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

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

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

    51 

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

    53 

    54   result_type operator()()

    55   {

    56     if(_n >= returned_block) {

    57       // discard values of random number generator

    58       for( ; _n < total_block; ++_n)

    59         _rng();

    60       _n = 0;

    61     }

    62     ++_n;

    63     return _rng();

    64   }

    65 

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

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

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

    69 

    70 #ifndef BOOST_NO_OPERATORS_IN_NAMESPACE

    71 

    72 #ifndef BOOST_NO_MEMBER_TEMPLATE_FRIENDS

    73   template<class CharT, class Traits>

    74   friend std::basic_ostream<CharT,Traits>&

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

    76   {

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

    78     return os;

    79   }

    80 

    81   template<class CharT, class Traits>

    82   friend std::basic_istream<CharT,Traits>&

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

    84   {

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

    86     return is;

    87   }

    88 #endif

    89 

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

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

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

    93   { return !(x == y); }

    94 #else

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

    96   bool operator==(const discard_block& rhs) const

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

    98   bool operator!=(const discard_block& rhs) const

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

   100 #endif

   101 

   102 private:

   103   base_type _rng;

   104   unsigned int _n;

   105 };

   106 

   107 #ifndef BOOST_NO_INCLASS_MEMBER_INITIALIZATION

   108 //  A definition is required even for integral static constants

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

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

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

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

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

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

   115 #endif

   116 

   117 } // namespace random

   118 

   119 } // namespace boost

   120 

   121 #endif // BOOST_RANDOM_DISCARD_BLOCK_HPP