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 {
32 public:
33 // types
34 typedef _RealType result_type;
35
36 class _LIBCPP_TEMPLATE_VIS param_type
37 {
38 result_type __lambda_;
39 public:
40 typedef exponential_distribution distribution_type;
41
42 _LIBCPP_INLINE_VISIBILITY
__lambda_(__lambda)43 explicit param_type(result_type __lambda = 1) : __lambda_(__lambda) {}
44
45 _LIBCPP_INLINE_VISIBILITY
lambda()46 result_type lambda() const {return __lambda_;}
47
48 friend _LIBCPP_INLINE_VISIBILITY
49 bool operator==(const param_type& __x, const param_type& __y)
50 {return __x.__lambda_ == __y.__lambda_;}
51 friend _LIBCPP_INLINE_VISIBILITY
52 bool operator!=(const param_type& __x, const param_type& __y)
53 {return !(__x == __y);}
54 };
55
56 private:
57 param_type __p_;
58
59 public:
60 // constructors and reset functions
61 #ifndef _LIBCPP_CXX03_LANG
62 _LIBCPP_INLINE_VISIBILITY
exponential_distribution()63 exponential_distribution() : exponential_distribution(1) {}
64 _LIBCPP_INLINE_VISIBILITY
exponential_distribution(result_type __lambda)65 explicit exponential_distribution(result_type __lambda)
66 : __p_(param_type(__lambda)) {}
67 #else
68 _LIBCPP_INLINE_VISIBILITY
69 explicit exponential_distribution(result_type __lambda = 1)
70 : __p_(param_type(__lambda)) {}
71 #endif
72 _LIBCPP_INLINE_VISIBILITY
exponential_distribution(const param_type & __p)73 explicit exponential_distribution(const param_type& __p) : __p_(__p) {}
74 _LIBCPP_INLINE_VISIBILITY
reset()75 void reset() {}
76
77 // generating functions
78 template<class _URNG>
79 _LIBCPP_INLINE_VISIBILITY
operator()80 result_type operator()(_URNG& __g)
81 {return (*this)(__g, __p_);}
82 template<class _URNG> result_type operator()(_URNG& __g, const param_type& __p);
83
84 // property functions
85 _LIBCPP_INLINE_VISIBILITY
lambda()86 result_type lambda() const {return __p_.lambda();}
87
88 _LIBCPP_INLINE_VISIBILITY
param()89 param_type param() const {return __p_;}
90 _LIBCPP_INLINE_VISIBILITY
param(const param_type & __p)91 void param(const param_type& __p) {__p_ = __p;}
92
93 _LIBCPP_INLINE_VISIBILITY
min()94 result_type min() const {return 0;}
95 _LIBCPP_INLINE_VISIBILITY
max()96 result_type max() const {return numeric_limits<result_type>::infinity();}
97
98 friend _LIBCPP_INLINE_VISIBILITY
99 bool operator==(const exponential_distribution& __x,
100 const exponential_distribution& __y)
101 {return __x.__p_ == __y.__p_;}
102 friend _LIBCPP_INLINE_VISIBILITY
103 bool operator!=(const exponential_distribution& __x,
104 const exponential_distribution& __y)
105 {return !(__x == __y);}
106 };
107
108 template <class _RealType>
109 template<class _URNG>
110 _RealType
operator()111 exponential_distribution<_RealType>::operator()(_URNG& __g, const param_type& __p)
112 {
113 static_assert(__libcpp_random_is_valid_urng<_URNG>::value, "");
114 return -_VSTD::log
115 (
116 result_type(1) -
117 _VSTD::generate_canonical<result_type,
118 numeric_limits<result_type>::digits>(__g)
119 )
120 / __p.lambda();
121 }
122
123 template <class _CharT, class _Traits, class _RealType>
124 _LIBCPP_HIDE_FROM_ABI basic_ostream<_CharT, _Traits>&
125 operator<<(basic_ostream<_CharT, _Traits>& __os,
126 const exponential_distribution<_RealType>& __x)
127 {
128 __save_flags<_CharT, _Traits> __lx(__os);
129 typedef basic_ostream<_CharT, _Traits> _OStream;
130 __os.flags(_OStream::dec | _OStream::left | _OStream::fixed |
131 _OStream::scientific);
132 return __os << __x.lambda();
133 }
134
135 template <class _CharT, class _Traits, class _RealType>
136 _LIBCPP_HIDE_FROM_ABI basic_istream<_CharT, _Traits>&
137 operator>>(basic_istream<_CharT, _Traits>& __is,
138 exponential_distribution<_RealType>& __x)
139 {
140 typedef exponential_distribution<_RealType> _Eng;
141 typedef typename _Eng::result_type result_type;
142 typedef typename _Eng::param_type param_type;
143 __save_flags<_CharT, _Traits> __lx(__is);
144 typedef basic_istream<_CharT, _Traits> _Istream;
145 __is.flags(_Istream::dec | _Istream::skipws);
146 result_type __lambda;
147 __is >> __lambda;
148 if (!__is.fail())
149 __x.param(param_type(__lambda));
150 return __is;
151 }
152
153 _LIBCPP_END_NAMESPACE_STD
154
155 _LIBCPP_POP_MACROS
156
157 #endif // _LIBCPP___RANDOM_EXPONENTIAL_DISTRIBUTION_H
158