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      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
     87