1 // Class template uniform_int_distribution -*- C++ -*-
3 // Copyright (C) 2009-2016 Free Software Foundation, Inc.
5 // This file is part of the GNU ISO C++ Library. This library is free
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26 * @file bits/uniform_int_dist.h
27 * This is an internal header file, included by other library headers.
28 * Do not attempt to use it directly. @headername{random}
31 #ifndef _GLIBCXX_BITS_UNIFORM_INT_DIST_H
32 #define _GLIBCXX_BITS_UNIFORM_INT_DIST_H
34 #include <type_traits>
37 namespace std _GLIBCXX_VISIBILITY(default)
39 _GLIBCXX_BEGIN_NAMESPACE_VERSION
43 /* Determine whether number is a power of 2. */
44 template<typename _Tp>
48 return ((__x - 1) & __x) == 0;
53 * @brief Uniform discrete distribution for random numbers.
55 * A discrete random distribution on the range @f$[min, max]@f$ with equal
56 * probability throughout the range.
58 * @ingroup random_distributions_uniform
60 template<typename _IntType = int>
61 class uniform_int_distribution
63 static_assert(std::is_integral<_IntType>::value,
64 "template argument not an integral type");
67 /** The type of the range of the distribution. */
68 typedef _IntType result_type;
69 /** Parameter type. */
72 typedef uniform_int_distribution<_IntType> distribution_type;
75 param_type(_IntType __a = 0,
76 _IntType __b = std::numeric_limits<_IntType>::max())
77 : _M_a(__a), _M_b(__b)
79 _GLIBCXX_DEBUG_ASSERT(_M_a <= _M_b);
91 operator==(const param_type& __p1, const param_type& __p2)
92 { return __p1._M_a == __p2._M_a && __p1._M_b == __p2._M_b; }
101 * @brief Constructs a uniform distribution object.
104 uniform_int_distribution(_IntType __a = 0,
105 _IntType __b = std::numeric_limits<_IntType>::max())
110 uniform_int_distribution(const param_type& __p)
115 * @brief Resets the distribution state.
117 * Does nothing for the uniform integer distribution.
124 { return _M_param.a(); }
128 { return _M_param.b(); }
131 * @brief Returns the parameter set of the distribution.
138 * @brief Sets the parameter set of the distribution.
139 * @param __param The new parameter set of the distribution.
142 param(const param_type& __param)
143 { _M_param = __param; }
146 * @brief Returns the inclusive lower bound of the distribution range.
150 { return this->a(); }
153 * @brief Returns the inclusive upper bound of the distribution range.
157 { return this->b(); }
160 * @brief Generating functions.
162 template<typename _UniformRandomNumberGenerator>
164 operator()(_UniformRandomNumberGenerator& __urng)
165 { return this->operator()(__urng, _M_param); }
167 template<typename _UniformRandomNumberGenerator>
169 operator()(_UniformRandomNumberGenerator& __urng,
170 const param_type& __p);
172 template<typename _ForwardIterator,
173 typename _UniformRandomNumberGenerator>
175 __generate(_ForwardIterator __f, _ForwardIterator __t,
176 _UniformRandomNumberGenerator& __urng)
177 { this->__generate(__f, __t, __urng, _M_param); }
179 template<typename _ForwardIterator,
180 typename _UniformRandomNumberGenerator>
182 __generate(_ForwardIterator __f, _ForwardIterator __t,
183 _UniformRandomNumberGenerator& __urng,
184 const param_type& __p)
185 { this->__generate_impl(__f, __t, __urng, __p); }
187 template<typename _UniformRandomNumberGenerator>
189 __generate(result_type* __f, result_type* __t,
190 _UniformRandomNumberGenerator& __urng,
191 const param_type& __p)
192 { this->__generate_impl(__f, __t, __urng, __p); }
195 * @brief Return true if two uniform integer distributions have
196 * the same parameters.
199 operator==(const uniform_int_distribution& __d1,
200 const uniform_int_distribution& __d2)
201 { return __d1._M_param == __d2._M_param; }
204 template<typename _ForwardIterator,
205 typename _UniformRandomNumberGenerator>
207 __generate_impl(_ForwardIterator __f, _ForwardIterator __t,
208 _UniformRandomNumberGenerator& __urng,
209 const param_type& __p);
214 template<typename _IntType>
215 template<typename _UniformRandomNumberGenerator>
216 typename uniform_int_distribution<_IntType>::result_type
217 uniform_int_distribution<_IntType>::
218 operator()(_UniformRandomNumberGenerator& __urng,
219 const param_type& __param)
221 typedef typename _UniformRandomNumberGenerator::result_type
223 typedef typename std::make_unsigned<result_type>::type __utype;
224 typedef typename std::common_type<_Gresult_type, __utype>::type
227 const __uctype __urngmin = __urng.min();
228 const __uctype __urngmax = __urng.max();
229 const __uctype __urngrange = __urngmax - __urngmin;
230 const __uctype __urange
231 = __uctype(__param.b()) - __uctype(__param.a());
235 if (__urngrange > __urange)
238 const __uctype __uerange = __urange + 1; // __urange can be zero
239 const __uctype __scaling = __urngrange / __uerange;
240 const __uctype __past = __uerange * __scaling;
242 __ret = __uctype(__urng()) - __urngmin;
243 while (__ret >= __past);
246 else if (__urngrange < __urange)
250 Note that every value in [0, urange]
251 can be written uniquely as
253 (urngrange + 1) * high + low
257 high in [0, urange / (urngrange + 1)]
261 low in [0, urngrange].
263 __uctype __tmp; // wraparound control
266 const __uctype __uerngrange = __urngrange + 1;
267 __tmp = (__uerngrange * operator()
268 (__urng, param_type(0, __urange / __uerngrange)));
269 __ret = __tmp + (__uctype(__urng()) - __urngmin);
271 while (__ret > __urange || __ret < __tmp);
274 __ret = __uctype(__urng()) - __urngmin;
276 return __ret + __param.a();
280 template<typename _IntType>
281 template<typename _ForwardIterator,
282 typename _UniformRandomNumberGenerator>
284 uniform_int_distribution<_IntType>::
285 __generate_impl(_ForwardIterator __f, _ForwardIterator __t,
286 _UniformRandomNumberGenerator& __urng,
287 const param_type& __param)
289 __glibcxx_function_requires(_ForwardIteratorConcept<_ForwardIterator>)
290 typedef typename _UniformRandomNumberGenerator::result_type
292 typedef typename std::make_unsigned<result_type>::type __utype;
293 typedef typename std::common_type<_Gresult_type, __utype>::type
296 const __uctype __urngmin = __urng.min();
297 const __uctype __urngmax = __urng.max();
298 const __uctype __urngrange = __urngmax - __urngmin;
299 const __uctype __urange
300 = __uctype(__param.b()) - __uctype(__param.a());
304 if (__urngrange > __urange)
306 if (__detail::_Power_of_2(__urngrange + 1)
307 && __detail::_Power_of_2(__urange + 1))
311 __ret = __uctype(__urng()) - __urngmin;
312 *__f++ = (__ret & __urange) + __param.a();
318 const __uctype __uerange = __urange + 1; // __urange can be zero
319 const __uctype __scaling = __urngrange / __uerange;
320 const __uctype __past = __uerange * __scaling;
324 __ret = __uctype(__urng()) - __urngmin;
325 while (__ret >= __past);
326 *__f++ = __ret / __scaling + __param.a();
330 else if (__urngrange < __urange)
334 Note that every value in [0, urange]
335 can be written uniquely as
337 (urngrange + 1) * high + low
341 high in [0, urange / (urngrange + 1)]
345 low in [0, urngrange].
347 __uctype __tmp; // wraparound control
352 const __uctype __uerngrange = __urngrange + 1;
353 __tmp = (__uerngrange * operator()
354 (__urng, param_type(0, __urange / __uerngrange)));
355 __ret = __tmp + (__uctype(__urng()) - __urngmin);
357 while (__ret > __urange || __ret < __tmp);
363 *__f++ = __uctype(__urng()) - __urngmin + __param.a();
366 _GLIBCXX_END_NAMESPACE_VERSION