boost/random/discard_block.hpp

   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  * $Id$
  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 #include <boost/random/detail/config.hpp>
  24
  25
  26 namespace boost {
  27 namespace random {
  28
  29 template<class UniformRandomNumberGenerator, unsigned int p, unsigned int r>
  30 class discard_block
  31 {
  32 public:
  33   typedef UniformRandomNumberGenerator base_type;
  34   typedef typename base_type::result_type result_type;
  35
  36   BOOST_STATIC_CONSTANT(bool, has_fixed_range = false);
  37   BOOST_STATIC_CONSTANT(unsigned int, total_block = p);
  38   BOOST_STATIC_CONSTANT(unsigned int, returned_block = r);
  39
  40 #ifndef BOOST_NO_LIMITS_COMPILE_TIME_CONSTANTS
  41   BOOST_STATIC_ASSERT(total_block >= returned_block);
  42 #endif
  43
  44   discard_block() : _rng(), _n(0) { }
  45   explicit discard_block(const base_type & rng) : _rng(rng), _n(0) { }
  46   template<class It> discard_block(It& first, It last)
  47     : _rng(first, last), _n(0) { }
  48   void seed() { _rng.seed(); _n = 0; }
  49   template<class T> void seed(T s) { _rng.seed(s); _n = 0; }
  50   template<class It> void seed(It& first, It last)
  51   { _n = 0; _rng.seed(first, last); }
  52
  53   const base_type& base() const { return _rng; }
  54
  55   result_type operator()()
  56   {
  57     if(_n >= returned_block) {
  58       // discard values of random number generator
  59       for( ; _n < total_block; ++_n)
  60         _rng();
  61       _n = 0;
  62     }
  63     ++_n;
  64     return _rng();
  65   }
  66
  67   result_type min BOOST_PREVENT_MACRO_SUBSTITUTION () const { return (_rng.min)(); }
  68   result_type max BOOST_PREVENT_MACRO_SUBSTITUTION () const { return (_rng.max)(); }
  69   static bool validation(result_type x) { return true; }  // dummy
  70
  71 #ifndef BOOST_NO_OPERATORS_IN_NAMESPACE
  72
  73 #ifndef BOOST_RANDOM_NO_STREAM_OPERATORS
  74   template<class CharT, class Traits>
  75   friend std::basic_ostream<CharT,Traits>&
  76   operator<<(std::basic_ostream<CharT,Traits>& os, const discard_block& s)
  77   {
  78     os << s._rng << " " << s._n << " ";
  79     return os;
  80   }
  81
  82   template<class CharT, class Traits>
  83   friend std::basic_istream<CharT,Traits>&
  84   operator>>(std::basic_istream<CharT,Traits>& is, discard_block& s)
  85   {
  86     is >> s._rng >> std::ws >> s._n >> std::ws;
  87     return is;
  88   }
  89 #endif
  90
  91   friend bool operator==(const discard_block& x, const discard_block& y)
  92   { return x._rng == y._rng && x._n == y._n; }
  93   friend bool operator!=(const discard_block& x, const discard_block& y)
  94   { return !(x == y); }
  95 #else
  96   // Use a member function; Streamable concept not supported.
  97   bool operator==(const discard_block& rhs) const
  98   { return _rng == rhs._rng && _n == rhs._n; }
  99   bool operator!=(const discard_block& rhs) const
 100   { return !(*this == rhs); }
 101 #endif
 102
 103 private:
 104   base_type _rng;
 105   unsigned int _n;
 106 };
 107
 108 #ifndef BOOST_NO_INCLASS_MEMBER_INITIALIZATION
 109 //  A definition is required even for integral static constants
 110 template<class UniformRandomNumberGenerator, unsigned int p, unsigned int r>
 111 const bool discard_block<UniformRandomNumberGenerator, p, r>::has_fixed_range;
 112 template<class UniformRandomNumberGenerator, unsigned int p, unsigned int r>
 113 const unsigned int discard_block<UniformRandomNumberGenerator, p, r>::total_block;
 114 template<class UniformRandomNumberGenerator, unsigned int p, unsigned int r>
 115 const unsigned int discard_block<UniformRandomNumberGenerator, p, r>::returned_block;
 116 #endif
 117
 118 } // namespace random
 119
 120 } // namespace boost
 121
 122 #endif // BOOST_RANDOM_DISCARD_BLOCK_HPP