1 //===----------------------------------------------------------------------===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 9 #ifndef _LIBCPP___ALGORITHM_RANGES_UNIFORM_RANDOM_BIT_GENERATOR_ADAPTOR_H 10 #define _LIBCPP___ALGORITHM_RANGES_UNIFORM_RANDOM_BIT_GENERATOR_ADAPTOR_H 11 12 #include <__config> 13 #include <__functional/invoke.h> 14 #include <__type_traits/remove_cvref.h> 15 16 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 17 # pragma GCC system_header 18 #endif 19 20 #if _LIBCPP_STD_VER >= 20 21 22 _LIBCPP_PUSH_MACROS 23 # include <__undef_macros> 24 25 _LIBCPP_BEGIN_NAMESPACE_STD 26 27 // Range versions of random algorithms (e.g. `std::shuffle`) are less constrained than their classic counterparts. 28 // Range algorithms only require the given generator to satisfy the `std::uniform_random_bit_generator` concept. 29 // Classic algorithms require the given generator to meet the uniform random bit generator requirements; these 30 // requirements include satisfying `std::uniform_random_bit_generator` and add a requirement for the generator to 31 // provide a nested `result_type` typedef (see `[rand.req.urng]`). 32 // 33 // To be able to reuse classic implementations, make the given generator meet the classic requirements by wrapping 34 // it into an adaptor type that forwards all of its interface and adds the required typedef. 35 template <class _Gen> 36 class _ClassicGenAdaptor { 37 private: 38 // The generator is not required to be copyable or movable, so it has to be stored as a reference. 39 _Gen& __gen_; 40 41 public: 42 using result_type = invoke_result_t<_Gen&>; 43 44 _LIBCPP_HIDE_FROM_ABI static constexpr auto min() { return __remove_cvref_t<_Gen>::min(); } 45 _LIBCPP_HIDE_FROM_ABI static constexpr auto max() { return __remove_cvref_t<_Gen>::max(); } 46 47 _LIBCPP_HIDE_FROM_ABI constexpr explicit _ClassicGenAdaptor(_Gen& __g) : __gen_(__g) {} 48 49 _LIBCPP_HIDE_FROM_ABI constexpr auto operator()() const { return __gen_(); } 50 }; 51 52 _LIBCPP_END_NAMESPACE_STD 53 54 _LIBCPP_POP_MACROS 55 56 #endif // _LIBCPP_STD_VER >= 20 57 58 #endif // _LIBCPP___ALGORITHM_RANGES_UNIFORM_RANDOM_BIT_GENERATOR_ADAPTOR_H 59