237 lines
6.9 KiB
C++
Executable File
237 lines
6.9 KiB
C++
Executable File
/* boost random/uniform_smallint.hpp header file
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*
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* Copyright Jens Maurer 2000-2001
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* Distributed under the Boost Software License, Version 1.0. (See
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* accompanying file LICENSE_1_0.txt or copy at
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* http://www.boost.org/LICENSE_1_0.txt)
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*
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* See http://www.boost.org for most recent version including documentation.
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*
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* $Id: uniform_smallint.hpp 47233 2008-07-08 16:22:46Z steven_watanabe $
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*
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* Revision history
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* 2001-04-08 added min<max assertion (N. Becker)
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* 2001-02-18 moved to individual header files
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*/
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#ifndef BOOST_RANDOM_UNIFORM_SMALLINT_HPP
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#define BOOST_RANDOM_UNIFORM_SMALLINT_HPP
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#include <cassert>
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#include <iostream>
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#include <boost/config.hpp>
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#include <boost/limits.hpp>
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#include <boost/static_assert.hpp>
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#include <boost/random/uniform_01.hpp>
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#include <boost/detail/workaround.hpp>
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#ifdef BOOST_NO_LIMITS_COMPILE_TIME_CONSTANTS
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#include <boost/type_traits/is_float.hpp>
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#endif
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namespace boost {
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// uniform integer distribution on a small range [min, max]
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namespace detail {
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template <class InputStream, class UniformInt, class Impl>
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InputStream& extract_uniform_int(InputStream& is, UniformInt& ud, Impl& impl)
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{
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typename UniformInt::result_type min, max;
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is >> std::ws >> min >> std::ws >> max;
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impl.set(min, max);
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return is;
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}
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template<class UniformRandomNumberGenerator, class IntType>
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struct uniform_smallint_integer
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{
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public:
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typedef UniformRandomNumberGenerator base_type;
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typedef IntType result_type;
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uniform_smallint_integer(base_type & rng, IntType min_arg, IntType max_arg)
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: _rng(&rng)
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{ set(min_arg, max_arg); }
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void set(result_type min, result_type max);
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result_type min BOOST_PREVENT_MACRO_SUBSTITUTION () const { return _min; }
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result_type max BOOST_PREVENT_MACRO_SUBSTITUTION () const { return _max; }
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base_type& base() const { return *_rng; }
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result_type operator()()
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{
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// we must not use the low bits here, because LCGs get very bad then
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return (((*_rng)() - (_rng->min)()) / _factor) % _range + _min;
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}
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private:
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typedef typename base_type::result_type base_result;
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base_type * _rng;
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IntType _min, _max;
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base_result _range;
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base_result _factor;
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};
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template<class UniformRandomNumberGenerator, class IntType>
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void uniform_smallint_integer<UniformRandomNumberGenerator, IntType>::
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set(result_type min_arg, result_type max_arg)
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{
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_min = min_arg;
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_max = max_arg;
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assert(min_arg <= max_arg);
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_range = static_cast<base_result>(_max-_min)+1;
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_factor = 1;
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// LCGs get bad when only taking the low bits.
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// (probably put this logic into a partial template specialization)
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// Check how many low bits we can ignore before we get too much
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// quantization error.
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base_result r_base = (_rng->max)() - (_rng->min)();
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if(r_base == (std::numeric_limits<base_result>::max)()) {
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_factor = 2;
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r_base /= 2;
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}
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r_base += 1;
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if(r_base % _range == 0) {
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// No quantization effects, good
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_factor = r_base / _range;
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} else {
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// carefully avoid overflow; pessimizing heree
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for( ; r_base/_range/32 >= _range; _factor *= 2)
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r_base /= 2;
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}
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}
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template<class UniformRandomNumberGenerator, class IntType>
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class uniform_smallint_float
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{
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public:
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typedef UniformRandomNumberGenerator base_type;
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typedef IntType result_type;
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uniform_smallint_float(base_type & rng, IntType min_arg, IntType max_arg)
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: _rng(rng)
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{
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// MSVC fails BOOST_STATIC_ASSERT with std::numeric_limits at class scope
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#if !defined(BOOST_NO_LIMITS_COMPILE_TIME_CONSTANTS) && !(defined(BOOST_MSVC) && BOOST_MSVC <= 1300)
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BOOST_STATIC_ASSERT(std::numeric_limits<IntType>::is_integer);
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BOOST_STATIC_ASSERT(!std::numeric_limits<typename base_type::result_type>::is_integer);
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#endif
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assert(min_arg <= max_arg);
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set(min_arg, max_arg);
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}
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void set(result_type min_arg, result_type max_arg)
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{
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_min = min_arg;
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_max = max_arg;
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_range = static_cast<base_result>(_max-_min)+1;
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}
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result_type min BOOST_PREVENT_MACRO_SUBSTITUTION () const { return _min; }
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result_type max BOOST_PREVENT_MACRO_SUBSTITUTION () const { return _max; }
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base_type& base() const { return _rng.base(); }
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result_type operator()()
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{
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return static_cast<IntType>(_rng() * _range) + _min;
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}
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private:
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typedef typename base_type::result_type base_result;
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uniform_01<base_type> _rng;
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IntType _min, _max;
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base_result _range;
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};
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} // namespace detail
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template<class IntType = int>
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class uniform_smallint
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{
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public:
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typedef IntType input_type;
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typedef IntType result_type;
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explicit uniform_smallint(IntType min_arg = 0, IntType max_arg = 9)
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: _min(min_arg), _max(max_arg)
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{
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#ifndef BOOST_NO_LIMITS_COMPILE_TIME_CONSTANTS
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// MSVC fails BOOST_STATIC_ASSERT with std::numeric_limits at class scope
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BOOST_STATIC_ASSERT(std::numeric_limits<IntType>::is_integer);
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#endif
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}
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result_type min BOOST_PREVENT_MACRO_SUBSTITUTION () const { return _min; }
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result_type max BOOST_PREVENT_MACRO_SUBSTITUTION () const { return _max; }
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void reset() { }
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template<class Engine>
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result_type operator()(Engine& eng)
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{
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typedef typename Engine::result_type base_result;
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base_result _range = static_cast<base_result>(_max-_min)+1;
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base_result _factor = 1;
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// LCGs get bad when only taking the low bits.
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// (probably put this logic into a partial template specialization)
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// Check how many low bits we can ignore before we get too much
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// quantization error.
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base_result r_base = (eng.max)() - (eng.min)();
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if(r_base == (std::numeric_limits<base_result>::max)()) {
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_factor = 2;
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r_base /= 2;
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}
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r_base += 1;
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if(r_base % _range == 0) {
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// No quantization effects, good
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_factor = r_base / _range;
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} else {
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// carefully avoid overflow; pessimizing heree
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for( ; r_base/_range/32 >= _range; _factor *= 2)
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r_base /= 2;
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}
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return ((eng() - (eng.min)()) / _factor) % _range + _min;
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}
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#if !defined(BOOST_NO_OPERATORS_IN_NAMESPACE) && !defined(BOOST_NO_MEMBER_TEMPLATE_FRIENDS)
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template<class CharT, class Traits>
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friend std::basic_ostream<CharT,Traits>&
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operator<<(std::basic_ostream<CharT,Traits>& os, const uniform_smallint& ud)
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{
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os << ud._min << " " << ud._max;
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return os;
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}
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template<class CharT, class Traits>
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friend std::basic_istream<CharT,Traits>&
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operator>>(std::basic_istream<CharT,Traits>& is, uniform_smallint& ud)
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{
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# if BOOST_WORKAROUND(_MSC_FULL_VER, BOOST_TESTED_AT(13102292)) && BOOST_MSVC > 1300
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return detail::extract_uniform_int(is, ud, ud._impl);
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# else
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is >> std::ws >> ud._min >> std::ws >> ud._max;
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return is;
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# endif
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}
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#endif
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private:
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result_type _min;
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result_type _max;
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};
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} // namespace boost
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#endif // BOOST_RANDOM_UNIFORM_SMALLINT_HPP
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