libstdc++: random Source File

libstdc++

experimental/random
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1// <experimental/random> -*- C++ -*-
2
3// Copyright (C) 2015-2026 Free Software Foundation, Inc.
4//
5// This file is part of the GNU ISO C++ Library. This library is free
6// software; you can redistribute it and/or modify it under the
7// terms of the GNU General Public License as published by the
8// Free Software Foundation; either version 3, or (at your option)
9// any later version.
10
11// This library is distributed in the hope that it will be useful,
12// but WITHOUT ANY WARRANTY; without even the implied warranty of
13// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14// GNU General Public License for more details.
15
16// Under Section 7 of GPL version 3, you are granted additional
17// permissions described in the GCC Runtime Library Exception, version
18// 3.1, as published by the Free Software Foundation.
19
20// You should have received a copy of the GNU General Public License and
21// a copy of the GCC Runtime Library Exception along with this program;
22// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
23// <http://www.gnu.org/licenses/>.
24
25/** @file experimental/random
26 * This is a TS C++ Library header.
27 * @ingroup libfund-ts
28 */
29
30#ifndef _GLIBCXX_EXPERIMENTAL_RANDOM
31#define _GLIBCXX_EXPERIMENTAL_RANDOM 1
32
33#include <bits/requires_hosted.h> // experimental is currently omitted
34
35#if __cplusplus >= 201402L
36#include <random>
37#include <experimental/bits/lfts_config.h>
38
39namespace std {
40_GLIBCXX_BEGIN_NAMESPACE_VERSION
41
42namespace experimental {
43inline namespace fundamentals_v2 {
44#define __cpp_lib_experimental_randint 201511
45
46 inline std::default_random_engine&
47 _S_randint_engine()
48 {
49 static thread_local default_random_engine __eng{random_device{}()};
50 return __eng;
51 }
52
53 // 13.2.2.1, Function template randint
54 template<typename _IntType>
55 [[__nodiscard__]]
56 inline _IntType
57 randint(_IntType __a, _IntType __b)
58 {
59 static_assert(is_integral<_IntType>::value && sizeof(_IntType) > 1,
60 "argument must be an integer type");
61 using _Dist = std::uniform_int_distribution<_IntType>;
62 // This relies on the fact our uniform_int_distribution is stateless,
63 // otherwise we'd need a static thread_local _Dist and pass it
64 // _Dist::param_type{__a, __b}.
65 return _Dist(__a, __b)(_S_randint_engine());
66 }
67
68 inline void
69 reseed()
70 {
71 _S_randint_engine().seed(random_device{}());
72 }
73
74 inline void
75 reseed(default_random_engine::result_type __value)
76 {
77 _S_randint_engine().seed(__value);
78 }
79} // namespace fundamentals_v2
80} // namespace experimental
81
82_GLIBCXX_END_NAMESPACE_VERSION
83} // namespace std
84
85#endif // C++14
86#endif // _GLIBCXX_EXPERIMENTAL_RANDOM
requires_hosted.h
lfts_config.h
std
ISO C++ entities toplevel namespace is std.
std::experimental
Namespace for features defined in ISO Technical Specifications.
std::linear_congruential_engine::seed
void seed(result_type __s=default_seed)
Reseeds the linear_congruential_engine random number generator engine sequence to the seed __s.
Definition bits/random.tcc:119
std::linear_congruential_engine< uint_fast32_t, 16807UL, 0UL, 2147483647UL >::result_type
uint_fast32_t result_type
Definition random.h:740
random