williamr@2: /* boost random/uniform_smallint.hpp header file
williamr@2:  *
williamr@2:  * Copyright Jens Maurer 2000-2001
williamr@2:  * Distributed under the Boost Software License, Version 1.0. (See
williamr@2:  * accompanying file LICENSE_1_0.txt or copy at
williamr@2:  * http://www.boost.org/LICENSE_1_0.txt)
williamr@2:  *
williamr@2:  * See http://www.boost.org for most recent version including documentation.
williamr@2:  *
williamr@2:  * $Id: uniform_smallint.hpp,v 1.29 2004/07/27 03:43:32 dgregor Exp $
williamr@2:  *
williamr@2:  * Revision history
williamr@2:  *  2001-04-08  added min<max assertion (N. Becker)
williamr@2:  *  2001-02-18  moved to individual header files
williamr@2:  */
williamr@2: 
williamr@2: #ifndef BOOST_RANDOM_UNIFORM_SMALLINT_HPP
williamr@2: #define BOOST_RANDOM_UNIFORM_SMALLINT_HPP
williamr@2: 
williamr@2: #include <cassert>
williamr@2: #include <iostream>
williamr@2: #include <boost/config.hpp>
williamr@2: #include <boost/limits.hpp>
williamr@2: #include <boost/static_assert.hpp>
williamr@2: #include <boost/random/uniform_01.hpp>
williamr@2: #include <boost/detail/workaround.hpp>
williamr@2: #ifdef BOOST_NO_LIMITS_COMPILE_TIME_CONSTANTS
williamr@2: #include <boost/type_traits/is_float.hpp>
williamr@2: #endif
williamr@2: 
williamr@2: 
williamr@2: namespace boost {
williamr@2: 
williamr@2: // uniform integer distribution on a small range [min, max]
williamr@2: 
williamr@2: namespace detail {
williamr@2: 
williamr@2: template <class InputStream, class UniformInt, class Impl>
williamr@2: InputStream& extract_uniform_int(InputStream& is, UniformInt& ud, Impl& impl)
williamr@2: {
williamr@2:     typename UniformInt::result_type min, max;
williamr@2:     is >> std::ws >> min >> std::ws >> max;
williamr@2:     impl.set(min, max);
williamr@2:     return is;
williamr@2: }
williamr@2: 
williamr@2: template<class UniformRandomNumberGenerator, class IntType>
williamr@2: struct uniform_smallint_integer
williamr@2: {
williamr@2: public:
williamr@2:   typedef UniformRandomNumberGenerator base_type;
williamr@2:   typedef IntType result_type;
williamr@2: 
williamr@2:   uniform_smallint_integer(base_type & rng, IntType min, IntType max)
williamr@2:     : _rng(&rng)
williamr@2:   { set(min, max); }
williamr@2: 
williamr@2:   void set(result_type min, result_type max);
williamr@2:   
williamr@2:   result_type min BOOST_PREVENT_MACRO_SUBSTITUTION () const { return _min; }
williamr@2:   result_type max BOOST_PREVENT_MACRO_SUBSTITUTION () const { return _max; }
williamr@2:   base_type& base() const { return *_rng; }
williamr@2:   
williamr@2:   result_type operator()()
williamr@2:   {
williamr@2:     // we must not use the low bits here, because LCGs get very bad then
williamr@2:     return (((*_rng)() - (_rng->min)()) / _factor) % _range + _min;
williamr@2:   }
williamr@2: 
williamr@2: private:
williamr@2:   typedef typename base_type::result_type base_result;
williamr@2:   base_type * _rng;
williamr@2:   IntType _min, _max;
williamr@2:   base_result _range;
williamr@2:   int _factor;
williamr@2: };
williamr@2: 
williamr@2: template<class UniformRandomNumberGenerator, class IntType>
williamr@2: void uniform_smallint_integer<UniformRandomNumberGenerator, IntType>::
williamr@2: set(result_type min, result_type max) 
williamr@2: {
williamr@2:   _min = min;
williamr@2:   _max = max;
williamr@2:   assert(min < max);
williamr@2: 
williamr@2:   _range = static_cast<base_result>(_max-_min)+1;
williamr@2:   base_result _factor = 1;
williamr@2:   
williamr@2:   // LCGs get bad when only taking the low bits.
williamr@2:   // (probably put this logic into a partial template specialization)
williamr@2:   // Check how many low bits we can ignore before we get too much
williamr@2:   // quantization error.
williamr@2:   base_result r_base = (_rng->max)() - (_rng->min)();
williamr@2:   if(r_base == (std::numeric_limits<base_result>::max)()) {
williamr@2:     _factor = 2;
williamr@2:     r_base /= 2;
williamr@2:   }
williamr@2:   r_base += 1;
williamr@2:   if(r_base % _range == 0) {
williamr@2:     // No quantization effects, good
williamr@2:     _factor = r_base / _range;
williamr@2:   } else {
williamr@2:     // carefully avoid overflow; pessimizing heree
williamr@2:     for( ; r_base/_range/32 >= _range; _factor *= 2)
williamr@2:       r_base /= 2;
williamr@2:   }
williamr@2: }
williamr@2: 
williamr@2: template<class UniformRandomNumberGenerator, class IntType>
williamr@2: class uniform_smallint_float
williamr@2: {
williamr@2: public:
williamr@2:   typedef UniformRandomNumberGenerator base_type;
williamr@2:   typedef IntType result_type;
williamr@2: 
williamr@2:   uniform_smallint_float(base_type & rng, IntType min, IntType max)
williamr@2:     : _rng(rng)
williamr@2:   {
williamr@2:     // MSVC fails BOOST_STATIC_ASSERT with std::numeric_limits at class scope
williamr@2: #if !defined(BOOST_NO_LIMITS_COMPILE_TIME_CONSTANTS) && !(defined(BOOST_MSVC) && BOOST_MSVC <= 1300)
williamr@2:     BOOST_STATIC_ASSERT(std::numeric_limits<IntType>::is_integer);
williamr@2:     BOOST_STATIC_ASSERT(!std::numeric_limits<typename base_type::result_type>::is_integer);
williamr@2: #endif
williamr@2: 
williamr@2:     assert(min < max);
williamr@2:     set(min, max);
williamr@2:   }
williamr@2: 
williamr@2:   void set(result_type min, result_type max)
williamr@2:   {
williamr@2:     _min = min;
williamr@2:     _max = max;
williamr@2:     _range = static_cast<base_result>(_max-_min)+1;
williamr@2:   }
williamr@2: 
williamr@2:   result_type min BOOST_PREVENT_MACRO_SUBSTITUTION () const { return _min; }
williamr@2:   result_type max BOOST_PREVENT_MACRO_SUBSTITUTION () const { return _max; }
williamr@2:   base_type& base() const { return _rng.base(); }
williamr@2: 
williamr@2:   result_type operator()()
williamr@2:   {
williamr@2:     return static_cast<IntType>(_rng() * _range) + _min;
williamr@2:   }
williamr@2: 
williamr@2: private:
williamr@2:   typedef typename base_type::result_type base_result;
williamr@2:   uniform_01<base_type> _rng;
williamr@2:   IntType _min, _max;
williamr@2:   base_result _range;
williamr@2: };
williamr@2: 
williamr@2: 
williamr@2: } // namespace detail
williamr@2: 
williamr@2: 
williamr@2: 
williamr@2: 
williamr@2: template<class IntType = int>
williamr@2: class uniform_smallint
williamr@2: {
williamr@2: public:
williamr@2:   typedef IntType input_type;
williamr@2:   typedef IntType result_type;
williamr@2: 
williamr@2:   explicit uniform_smallint(IntType min = 0, IntType max = 9)
williamr@2:     : _min(min), _max(max)
williamr@2:   {
williamr@2: #ifndef BOOST_NO_LIMITS_COMPILE_TIME_CONSTANTS
williamr@2:     // MSVC fails BOOST_STATIC_ASSERT with std::numeric_limits at class scope
williamr@2:     BOOST_STATIC_ASSERT(std::numeric_limits<IntType>::is_integer);
williamr@2: #endif
williamr@2:  }
williamr@2: 
williamr@2:   result_type min BOOST_PREVENT_MACRO_SUBSTITUTION () const { return _min; }
williamr@2:   result_type max BOOST_PREVENT_MACRO_SUBSTITUTION () const { return _max; }
williamr@2:   void reset() { }
williamr@2: 
williamr@2:   template<class Engine>
williamr@2:   result_type operator()(Engine& eng)
williamr@2:   {
williamr@2:     typedef typename Engine::result_type base_result;
williamr@2:     base_result _range = static_cast<base_result>(_max-_min)+1;
williamr@2:     base_result _factor = 1;
williamr@2:     
williamr@2:     // LCGs get bad when only taking the low bits.
williamr@2:     // (probably put this logic into a partial template specialization)
williamr@2:     // Check how many low bits we can ignore before we get too much
williamr@2:     // quantization error.
williamr@2:     base_result r_base = (eng.max)() - (eng.min)();
williamr@2:     if(r_base == (std::numeric_limits<base_result>::max)()) {
williamr@2:       _factor = 2;
williamr@2:       r_base /= 2;
williamr@2:     }
williamr@2:     r_base += 1;
williamr@2:     if(r_base % _range == 0) {
williamr@2:       // No quantization effects, good
williamr@2:       _factor = r_base / _range;
williamr@2:     } else {
williamr@2:       // carefully avoid overflow; pessimizing heree
williamr@2:       for( ; r_base/_range/32 >= _range; _factor *= 2)
williamr@2:         r_base /= 2;
williamr@2:     }
williamr@2: 
williamr@2:     return ((eng() - (eng.min)()) / _factor) % _range + _min;
williamr@2:   }
williamr@2: 
williamr@2: #if !defined(BOOST_NO_OPERATORS_IN_NAMESPACE) && !defined(BOOST_NO_MEMBER_TEMPLATE_FRIENDS)
williamr@2:   template<class CharT, class Traits>
williamr@2:   friend std::basic_ostream<CharT,Traits>&
williamr@2:   operator<<(std::basic_ostream<CharT,Traits>& os, const uniform_smallint& ud)
williamr@2:   {
williamr@2:     os << ud._min << " " << ud._max;
williamr@2:     return os;
williamr@2:   }
williamr@2: 
williamr@2:   template<class CharT, class Traits>
williamr@2:   friend std::basic_istream<CharT,Traits>&
williamr@2:   operator>>(std::basic_istream<CharT,Traits>& is, uniform_smallint& ud)
williamr@2:   {
williamr@2: # if BOOST_WORKAROUND(_MSC_FULL_VER, BOOST_TESTED_AT(13102292)) && BOOST_MSVC > 1300
williamr@2:       return detail::extract_uniform_int(is, ud, ud._impl);
williamr@2: # else
williamr@2:     is >> std::ws >> ud._min >> std::ws >> ud._max;
williamr@2:     return is;
williamr@2: # endif
williamr@2:   }
williamr@2: #endif
williamr@2: 
williamr@2: private:
williamr@2:   result_type _min;
williamr@2:   result_type _max;
williamr@2: };
williamr@2: 
williamr@2: } // namespace boost
williamr@2: 
williamr@2: #endif // BOOST_RANDOM_UNIFORM_SMALLINT_HPP