1 // Class template uniform_int_distribution -*- C++ -*-
3 // Copyright (C) 2009-2018 Free Software Foundation, Inc.
5 // This file is part of the GNU ISO C++ Library. This library is free
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7 // terms of the GNU General Public License as published by the
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16 // Under Section 7 of GPL version 3, you are granted additional
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18 // 3.1, as published by the Free Software Foundation.
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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.
54 * A discrete random distribution on the range @f$[min, max]@f$ with equal
55 * probability throughout the range.
57 template<typename _IntType
= int>
58 class uniform_int_distribution
60 static_assert(std::is_integral
<_IntType
>::value
,
61 "template argument must be an integral type");
64 /** The type of the range of the distribution. */
65 typedef _IntType result_type
;
66 /** Parameter type. */
69 typedef uniform_int_distribution
<_IntType
> distribution_type
;
72 param_type(_IntType __a
= 0,
73 _IntType __b
= std::numeric_limits
<_IntType
>::max())
74 : _M_a(__a
), _M_b(__b
)
76 __glibcxx_assert(_M_a
<= _M_b
);
88 operator==(const param_type
& __p1
, const param_type
& __p2
)
89 { return __p1
._M_a
== __p2
._M_a
&& __p1
._M_b
== __p2
._M_b
; }
92 operator!=(const param_type
& __p1
, const param_type
& __p2
)
93 { return !(__p1
== __p2
); }
102 * @brief Constructs a uniform distribution object.
105 uniform_int_distribution(_IntType __a
= 0,
106 _IntType __b
= std::numeric_limits
<_IntType
>::max())
111 uniform_int_distribution(const param_type
& __p
)
116 * @brief Resets the distribution state.
118 * Does nothing for the uniform integer distribution.
125 { return _M_param
.a(); }
129 { return _M_param
.b(); }
132 * @brief Returns the parameter set of the distribution.
139 * @brief Sets the parameter set of the distribution.
140 * @param __param The new parameter set of the distribution.
143 param(const param_type
& __param
)
144 { _M_param
= __param
; }
147 * @brief Returns the inclusive lower bound of the distribution range.
151 { return this->a(); }
154 * @brief Returns the inclusive upper bound of the distribution range.
158 { return this->b(); }
161 * @brief Generating functions.
163 template<typename _UniformRandomNumberGenerator
>
165 operator()(_UniformRandomNumberGenerator
& __urng
)
166 { return this->operator()(__urng
, _M_param
); }
168 template<typename _UniformRandomNumberGenerator
>
170 operator()(_UniformRandomNumberGenerator
& __urng
,
171 const param_type
& __p
);
173 template<typename _ForwardIterator
,
174 typename _UniformRandomNumberGenerator
>
176 __generate(_ForwardIterator __f
, _ForwardIterator __t
,
177 _UniformRandomNumberGenerator
& __urng
)
178 { this->__generate(__f
, __t
, __urng
, _M_param
); }
180 template<typename _ForwardIterator
,
181 typename _UniformRandomNumberGenerator
>
183 __generate(_ForwardIterator __f
, _ForwardIterator __t
,
184 _UniformRandomNumberGenerator
& __urng
,
185 const param_type
& __p
)
186 { this->__generate_impl(__f
, __t
, __urng
, __p
); }
188 template<typename _UniformRandomNumberGenerator
>
190 __generate(result_type
* __f
, result_type
* __t
,
191 _UniformRandomNumberGenerator
& __urng
,
192 const param_type
& __p
)
193 { this->__generate_impl(__f
, __t
, __urng
, __p
); }
196 * @brief Return true if two uniform integer distributions have
197 * the same parameters.
200 operator==(const uniform_int_distribution
& __d1
,
201 const uniform_int_distribution
& __d2
)
202 { return __d1
._M_param
== __d2
._M_param
; }
205 template<typename _ForwardIterator
,
206 typename _UniformRandomNumberGenerator
>
208 __generate_impl(_ForwardIterator __f
, _ForwardIterator __t
,
209 _UniformRandomNumberGenerator
& __urng
,
210 const param_type
& __p
);
215 template<typename _IntType
>
216 template<typename _UniformRandomNumberGenerator
>
217 typename uniform_int_distribution
<_IntType
>::result_type
218 uniform_int_distribution
<_IntType
>::
219 operator()(_UniformRandomNumberGenerator
& __urng
,
220 const param_type
& __param
)
222 typedef typename
_UniformRandomNumberGenerator::result_type
224 typedef typename
std::make_unsigned
<result_type
>::type __utype
;
225 typedef typename
std::common_type
<_Gresult_type
, __utype
>::type
228 const __uctype __urngmin
= __urng
.min();
229 const __uctype __urngmax
= __urng
.max();
230 const __uctype __urngrange
= __urngmax
- __urngmin
;
231 const __uctype __urange
232 = __uctype(__param
.b()) - __uctype(__param
.a());
236 if (__urngrange
> __urange
)
239 const __uctype __uerange
= __urange
+ 1; // __urange can be zero
240 const __uctype __scaling
= __urngrange
/ __uerange
;
241 const __uctype __past
= __uerange
* __scaling
;
243 __ret
= __uctype(__urng()) - __urngmin
;
244 while (__ret
>= __past
);
247 else if (__urngrange
< __urange
)
251 Note that every value in [0, urange]
252 can be written uniquely as
254 (urngrange + 1) * high + low
258 high in [0, urange / (urngrange + 1)]
262 low in [0, urngrange].
264 __uctype __tmp
; // wraparound control
267 const __uctype __uerngrange
= __urngrange
+ 1;
268 __tmp
= (__uerngrange
* operator()
269 (__urng
, param_type(0, __urange
/ __uerngrange
)));
270 __ret
= __tmp
+ (__uctype(__urng()) - __urngmin
);
272 while (__ret
> __urange
|| __ret
< __tmp
);
275 __ret
= __uctype(__urng()) - __urngmin
;
277 return __ret
+ __param
.a();
281 template<typename _IntType
>
282 template<typename _ForwardIterator
,
283 typename _UniformRandomNumberGenerator
>
285 uniform_int_distribution
<_IntType
>::
286 __generate_impl(_ForwardIterator __f
, _ForwardIterator __t
,
287 _UniformRandomNumberGenerator
& __urng
,
288 const param_type
& __param
)
290 __glibcxx_function_requires(_ForwardIteratorConcept
<_ForwardIterator
>)
291 typedef typename
_UniformRandomNumberGenerator::result_type
293 typedef typename
std::make_unsigned
<result_type
>::type __utype
;
294 typedef typename
std::common_type
<_Gresult_type
, __utype
>::type
297 const __uctype __urngmin
= __urng
.min();
298 const __uctype __urngmax
= __urng
.max();
299 const __uctype __urngrange
= __urngmax
- __urngmin
;
300 const __uctype __urange
301 = __uctype(__param
.b()) - __uctype(__param
.a());
305 if (__urngrange
> __urange
)
307 if (__detail::_Power_of_2(__urngrange
+ 1)
308 && __detail::_Power_of_2(__urange
+ 1))
312 __ret
= __uctype(__urng()) - __urngmin
;
313 *__f
++ = (__ret
& __urange
) + __param
.a();
319 const __uctype __uerange
= __urange
+ 1; // __urange can be zero
320 const __uctype __scaling
= __urngrange
/ __uerange
;
321 const __uctype __past
= __uerange
* __scaling
;
325 __ret
= __uctype(__urng()) - __urngmin
;
326 while (__ret
>= __past
);
327 *__f
++ = __ret
/ __scaling
+ __param
.a();
331 else if (__urngrange
< __urange
)
335 Note that every value in [0, urange]
336 can be written uniquely as
338 (urngrange + 1) * high + low
342 high in [0, urange / (urngrange + 1)]
346 low in [0, urngrange].
348 __uctype __tmp
; // wraparound control
353 const __uctype __uerngrange
= __urngrange
+ 1;
354 __tmp
= (__uerngrange
* operator()
355 (__urng
, param_type(0, __urange
/ __uerngrange
)));
356 __ret
= __tmp
+ (__uctype(__urng()) - __urngmin
);
358 while (__ret
> __urange
|| __ret
< __tmp
);
364 *__f
++ = __uctype(__urng()) - __urngmin
+ __param
.a();
367 // operator!= and operator<< and operator>> are defined in <bits/random.h>
369 _GLIBCXX_END_NAMESPACE_VERSION