libstdc++-v3/include/experimental/random

   1 // <experimental/random> -*- C++ -*-
   2
   3 // Copyright (C) 2015-2024 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
  39 namespace std {
  40 _GLIBCXX_BEGIN_NAMESPACE_VERSION
  41
  42 namespace experimental {
  43 inline 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