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1 | /* boost random/uniform_real_distribution.hpp header file |
2 | * | |
3 | * Copyright Jens Maurer 2000-2001 | |
4 | * Copyright Steven Watanabe 2011 | |
5 | * Distributed under the Boost Software License, Version 1.0. (See | |
6 | * accompanying file LICENSE_1_0.txt or copy at | |
7 | * http://www.boost.org/LICENSE_1_0.txt) | |
8 | * | |
9 | * See http://www.boost.org for most recent version including documentation. | |
10 | * | |
11 | * $Id$ | |
12 | * | |
13 | */ | |
14 | ||
15 | #ifndef BOOST_RANDOM_UNIFORM_REAL_DISTRIBUTION_HPP | |
16 | #define BOOST_RANDOM_UNIFORM_REAL_DISTRIBUTION_HPP | |
17 | ||
18 | #include <iosfwd> | |
19 | #include <ios> | |
20 | #include <istream> | |
21 | #include <boost/assert.hpp> | |
22 | #include <boost/config.hpp> | |
23 | #include <boost/random/detail/config.hpp> | |
24 | #include <boost/random/detail/operators.hpp> | |
25 | #include <boost/random/detail/signed_unsigned_tools.hpp> | |
26 | #include <boost/type_traits/is_integral.hpp> | |
7c673cae FG |
27 | |
28 | namespace boost { | |
29 | namespace random { | |
30 | namespace detail { | |
31 | ||
32 | template<class Engine, class T> | |
33 | T generate_uniform_real( | |
34 | Engine& eng, T min_value, T max_value, | |
20effc67 | 35 | boost::false_type /** is_integral<Engine::result_type> */) |
7c673cae FG |
36 | { |
37 | for(;;) { | |
38 | typedef T result_type; | |
39 | result_type numerator = static_cast<T>(eng() - (eng.min)()); | |
40 | result_type divisor = static_cast<T>((eng.max)() - (eng.min)()); | |
41 | BOOST_ASSERT(divisor > 0); | |
42 | BOOST_ASSERT(numerator >= 0 && numerator <= divisor); | |
43 | T result = numerator / divisor * (max_value - min_value) + min_value; | |
44 | if(result < max_value) return result; | |
45 | } | |
46 | } | |
47 | ||
48 | template<class Engine, class T> | |
49 | T generate_uniform_real( | |
50 | Engine& eng, T min_value, T max_value, | |
20effc67 | 51 | boost::true_type /** is_integral<Engine::result_type> */) |
7c673cae FG |
52 | { |
53 | for(;;) { | |
54 | typedef T result_type; | |
55 | typedef typename Engine::result_type base_result; | |
56 | result_type numerator = static_cast<T>(subtract<base_result>()(eng(), (eng.min)())); | |
57 | result_type divisor = static_cast<T>(subtract<base_result>()((eng.max)(), (eng.min)())) + 1; | |
58 | BOOST_ASSERT(divisor > 0); | |
59 | BOOST_ASSERT(numerator >= 0 && numerator <= divisor); | |
60 | T result = numerator / divisor * (max_value - min_value) + min_value; | |
61 | if(result < max_value) return result; | |
62 | } | |
63 | } | |
64 | ||
65 | template<class Engine, class T> | |
66 | inline T generate_uniform_real(Engine& eng, T min_value, T max_value) | |
67 | { | |
68 | if(max_value / 2 - min_value / 2 > (std::numeric_limits<T>::max)() / 2) | |
69 | return 2 * generate_uniform_real(eng, T(min_value / 2), T(max_value / 2)); | |
70 | typedef typename Engine::result_type base_result; | |
71 | return generate_uniform_real(eng, min_value, max_value, | |
72 | boost::is_integral<base_result>()); | |
73 | } | |
74 | ||
75 | } | |
76 | ||
77 | /** | |
78 | * The class template uniform_real_distribution models a \random_distribution. | |
79 | * On each invocation, it returns a random floating-point value uniformly | |
80 | * distributed in the range [min..max). | |
81 | */ | |
82 | template<class RealType = double> | |
83 | class uniform_real_distribution | |
84 | { | |
85 | public: | |
86 | typedef RealType input_type; | |
87 | typedef RealType result_type; | |
88 | ||
89 | class param_type | |
90 | { | |
91 | public: | |
92 | ||
93 | typedef uniform_real_distribution distribution_type; | |
94 | ||
95 | /** | |
96 | * Constructs the parameters of a uniform_real_distribution. | |
97 | * | |
98 | * Requires min <= max | |
99 | */ | |
100 | explicit param_type(RealType min_arg = RealType(0.0), | |
101 | RealType max_arg = RealType(1.0)) | |
102 | : _min(min_arg), _max(max_arg) | |
103 | { | |
104 | BOOST_ASSERT(_min < _max); | |
105 | } | |
106 | ||
107 | /** Returns the minimum value of the distribution. */ | |
108 | RealType a() const { return _min; } | |
109 | /** Returns the maximum value of the distribution. */ | |
110 | RealType b() const { return _max; } | |
111 | ||
112 | /** Writes the parameters to a @c std::ostream. */ | |
113 | BOOST_RANDOM_DETAIL_OSTREAM_OPERATOR(os, param_type, parm) | |
114 | { | |
115 | os << parm._min << " " << parm._max; | |
116 | return os; | |
117 | } | |
118 | ||
119 | /** Reads the parameters from a @c std::istream. */ | |
120 | BOOST_RANDOM_DETAIL_ISTREAM_OPERATOR(is, param_type, parm) | |
121 | { | |
122 | RealType min_in, max_in; | |
123 | if(is >> min_in >> std::ws >> max_in) { | |
124 | if(min_in <= max_in) { | |
125 | parm._min = min_in; | |
126 | parm._max = max_in; | |
127 | } else { | |
128 | is.setstate(std::ios_base::failbit); | |
129 | } | |
130 | } | |
131 | return is; | |
132 | } | |
133 | ||
134 | /** Returns true if the two sets of parameters are equal. */ | |
135 | BOOST_RANDOM_DETAIL_EQUALITY_OPERATOR(param_type, lhs, rhs) | |
136 | { return lhs._min == rhs._min && lhs._max == rhs._max; } | |
137 | ||
138 | /** Returns true if the two sets of parameters are different. */ | |
139 | BOOST_RANDOM_DETAIL_INEQUALITY_OPERATOR(param_type) | |
140 | ||
141 | private: | |
142 | ||
143 | RealType _min; | |
144 | RealType _max; | |
145 | }; | |
146 | ||
147 | /** | |
148 | * Constructs a uniform_real_distribution. @c min and @c max are | |
149 | * the parameters of the distribution. | |
150 | * | |
151 | * Requires: min <= max | |
152 | */ | |
153 | explicit uniform_real_distribution( | |
154 | RealType min_arg = RealType(0.0), | |
155 | RealType max_arg = RealType(1.0)) | |
156 | : _min(min_arg), _max(max_arg) | |
157 | { | |
158 | BOOST_ASSERT(min_arg < max_arg); | |
159 | } | |
160 | /** Constructs a uniform_real_distribution from its parameters. */ | |
161 | explicit uniform_real_distribution(const param_type& parm) | |
162 | : _min(parm.a()), _max(parm.b()) {} | |
163 | ||
164 | /** Returns the minimum value of the distribution */ | |
165 | RealType min BOOST_PREVENT_MACRO_SUBSTITUTION () const { return _min; } | |
166 | /** Returns the maximum value of the distribution */ | |
167 | RealType max BOOST_PREVENT_MACRO_SUBSTITUTION () const { return _max; } | |
168 | ||
169 | /** Returns the minimum value of the distribution */ | |
170 | RealType a() const { return _min; } | |
171 | /** Returns the maximum value of the distribution */ | |
172 | RealType b() const { return _max; } | |
173 | ||
174 | /** Returns the parameters of the distribution. */ | |
175 | param_type param() const { return param_type(_min, _max); } | |
176 | /** Sets the parameters of the distribution. */ | |
177 | void param(const param_type& parm) | |
178 | { | |
179 | _min = parm.a(); | |
180 | _max = parm.b(); | |
181 | } | |
182 | ||
183 | /** | |
184 | * Effects: Subsequent uses of the distribution do not depend | |
185 | * on values produced by any engine prior to invoking reset. | |
186 | */ | |
187 | void reset() { } | |
188 | ||
189 | /** Returns a value uniformly distributed in the range [min, max). */ | |
190 | template<class Engine> | |
191 | result_type operator()(Engine& eng) const | |
192 | { return detail::generate_uniform_real(eng, _min, _max); } | |
193 | ||
194 | /** | |
195 | * Returns a value uniformly distributed in the range | |
196 | * [param.a(), param.b()). | |
197 | */ | |
198 | template<class Engine> | |
199 | result_type operator()(Engine& eng, const param_type& parm) const | |
200 | { return detail::generate_uniform_real(eng, parm.a(), parm.b()); } | |
201 | ||
202 | /** Writes the distribution to a @c std::ostream. */ | |
203 | BOOST_RANDOM_DETAIL_OSTREAM_OPERATOR(os, uniform_real_distribution, ud) | |
204 | { | |
205 | os << ud.param(); | |
206 | return os; | |
207 | } | |
208 | ||
209 | /** Reads the distribution from a @c std::istream. */ | |
210 | BOOST_RANDOM_DETAIL_ISTREAM_OPERATOR(is, uniform_real_distribution, ud) | |
211 | { | |
212 | param_type parm; | |
213 | if(is >> parm) { | |
214 | ud.param(parm); | |
215 | } | |
216 | return is; | |
217 | } | |
218 | ||
219 | /** | |
220 | * Returns true if the two distributions will produce identical sequences | |
221 | * of values given equal generators. | |
222 | */ | |
223 | BOOST_RANDOM_DETAIL_EQUALITY_OPERATOR(uniform_real_distribution, lhs, rhs) | |
224 | { return lhs._min == rhs._min && lhs._max == rhs._max; } | |
225 | ||
226 | /** | |
227 | * Returns true if the two distributions may produce different sequences | |
228 | * of values given equal generators. | |
229 | */ | |
230 | BOOST_RANDOM_DETAIL_INEQUALITY_OPERATOR(uniform_real_distribution) | |
231 | ||
232 | private: | |
233 | RealType _min; | |
234 | RealType _max; | |
235 | }; | |
236 | ||
237 | } // namespace random | |
238 | } // namespace boost | |
239 | ||
240 | #endif // BOOST_RANDOM_UNIFORM_INT_HPP |