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___RANDOM_EXPONENTIAL_DISTRIBUTION_H 10 #define _LIBCPP___RANDOM_EXPONENTIAL_DISTRIBUTION_H 11 12 #include <__config> 13 #include <__random/generate_canonical.h> 14 #include <__random/is_valid.h> 15 #include <__random/uniform_real_distribution.h> 16 #include <cmath> 17 #include <iosfwd> 18 #include <limits> 19 20 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 21 # pragma GCC system_header 22 #endif 23 24 _LIBCPP_PUSH_MACROS 25 #include <__undef_macros> 26 27 _LIBCPP_BEGIN_NAMESPACE_STD 28 29 template <class _RealType = double> 30 class _LIBCPP_TEMPLATE_VIS exponential_distribution { 31 static_assert(__libcpp_random_is_valid_realtype<_RealType>::value, 32 "RealType must be a supported floating-point type"); 33 34 public: 35 // types 36 typedef _RealType result_type; 37 38 class _LIBCPP_TEMPLATE_VIS param_type { 39 result_type __lambda_; 40 41 public: 42 typedef exponential_distribution distribution_type; 43 44 _LIBCPP_HIDE_FROM_ABI explicit param_type(result_type __lambda = 1) : __lambda_(__lambda) {} 45 46 _LIBCPP_HIDE_FROM_ABI result_type lambda() const { return __lambda_; } 47 48 friend _LIBCPP_HIDE_FROM_ABI bool operator==(const param_type& __x, const param_type& __y) { 49 return __x.__lambda_ == __y.__lambda_; 50 } 51 friend _LIBCPP_HIDE_FROM_ABI bool operator!=(const param_type& __x, const param_type& __y) { return !(__x == __y); } 52 }; 53 54 private: 55 param_type __p_; 56 57 public: 58 // constructors and reset functions 59 #ifndef _LIBCPP_CXX03_LANG 60 _LIBCPP_HIDE_FROM_ABI exponential_distribution() : exponential_distribution(1) {} 61 _LIBCPP_HIDE_FROM_ABI explicit exponential_distribution(result_type __lambda) : __p_(param_type(__lambda)) {} 62 #else 63 _LIBCPP_HIDE_FROM_ABI explicit exponential_distribution(result_type __lambda = 1) : __p_(param_type(__lambda)) {} 64 #endif 65 _LIBCPP_HIDE_FROM_ABI explicit exponential_distribution(const param_type& __p) : __p_(__p) {} 66 _LIBCPP_HIDE_FROM_ABI void reset() {} 67 68 // generating functions 69 template <class _URNG> 70 _LIBCPP_HIDE_FROM_ABI result_type operator()(_URNG& __g) { 71 return (*this)(__g, __p_); 72 } 73 template <class _URNG> 74 _LIBCPP_HIDE_FROM_ABI result_type operator()(_URNG& __g, const param_type& __p); 75 76 // property functions 77 _LIBCPP_HIDE_FROM_ABI result_type lambda() const { return __p_.lambda(); } 78 79 _LIBCPP_HIDE_FROM_ABI param_type param() const { return __p_; } 80 _LIBCPP_HIDE_FROM_ABI void param(const param_type& __p) { __p_ = __p; } 81 82 _LIBCPP_HIDE_FROM_ABI result_type min() const { return 0; } 83 _LIBCPP_HIDE_FROM_ABI result_type max() const { return numeric_limits<result_type>::infinity(); } 84 85 friend _LIBCPP_HIDE_FROM_ABI bool 86 operator==(const exponential_distribution& __x, const exponential_distribution& __y) { 87 return __x.__p_ == __y.__p_; 88 } 89 friend _LIBCPP_HIDE_FROM_ABI bool 90 operator!=(const exponential_distribution& __x, const exponential_distribution& __y) { 91 return !(__x == __y); 92 } 93 }; 94 95 template <class _RealType> 96 template <class _URNG> 97 _RealType exponential_distribution<_RealType>::operator()(_URNG& __g, const param_type& __p) { 98 static_assert(__libcpp_random_is_valid_urng<_URNG>::value, ""); 99 return -std::log(result_type(1) - std::generate_canonical<result_type, numeric_limits<result_type>::digits>(__g)) / 100 __p.lambda(); 101 } 102 103 template <class _CharT, class _Traits, class _RealType> 104 _LIBCPP_HIDE_FROM_ABI basic_ostream<_CharT, _Traits>& 105 operator<<(basic_ostream<_CharT, _Traits>& __os, const exponential_distribution<_RealType>& __x) { 106 __save_flags<_CharT, _Traits> __lx(__os); 107 typedef basic_ostream<_CharT, _Traits> _OStream; 108 __os.flags(_OStream::dec | _OStream::left | _OStream::fixed | _OStream::scientific); 109 return __os << __x.lambda(); 110 } 111 112 template <class _CharT, class _Traits, class _RealType> 113 _LIBCPP_HIDE_FROM_ABI basic_istream<_CharT, _Traits>& 114 operator>>(basic_istream<_CharT, _Traits>& __is, exponential_distribution<_RealType>& __x) { 115 typedef exponential_distribution<_RealType> _Eng; 116 typedef typename _Eng::result_type result_type; 117 typedef typename _Eng::param_type param_type; 118 __save_flags<_CharT, _Traits> __lx(__is); 119 typedef basic_istream<_CharT, _Traits> _Istream; 120 __is.flags(_Istream::dec | _Istream::skipws); 121 result_type __lambda; 122 __is >> __lambda; 123 if (!__is.fail()) 124 __x.param(param_type(__lambda)); 125 return __is; 126 } 127 128 _LIBCPP_END_NAMESPACE_STD 129 130 _LIBCPP_POP_MACROS 131 132 #endif // _LIBCPP___RANDOM_EXPONENTIAL_DISTRIBUTION_H 133