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>
83 _LIBCPP_HIDE_FROM_ABI result_type operator()(_URNG& __g, const param_type& __p);
84
85 // property functions
86 _LIBCPP_INLINE_VISIBILITY
lambda()87 result_type lambda() const {return __p_.lambda();}
88
89 _LIBCPP_INLINE_VISIBILITY
param()90 param_type param() const {return __p_;}
91 _LIBCPP_INLINE_VISIBILITY
param(const param_type & __p)92 void param(const param_type& __p) {__p_ = __p;}
93
94 _LIBCPP_INLINE_VISIBILITY
min()95 result_type min() const {return 0;}
96 _LIBCPP_INLINE_VISIBILITY
max()97 result_type max() const {return numeric_limits<result_type>::infinity();}
98
99 friend _LIBCPP_INLINE_VISIBILITY
100 bool operator==(const exponential_distribution& __x,
101 const exponential_distribution& __y)
102 {return __x.__p_ == __y.__p_;}
103 friend _LIBCPP_INLINE_VISIBILITY
104 bool operator!=(const exponential_distribution& __x,
105 const exponential_distribution& __y)
106 {return !(__x == __y);}
107 };
108
109 template <class _RealType>
110 template<class _URNG>
111 _RealType
operator()112 exponential_distribution<_RealType>::operator()(_URNG& __g, const param_type& __p)
113 {
114 static_assert(__libcpp_random_is_valid_urng<_URNG>::value, "");
115 return -_VSTD::log
116 (
117 result_type(1) -
118 _VSTD::generate_canonical<result_type,
119 numeric_limits<result_type>::digits>(__g)
120 )
121 / __p.lambda();
122 }
123
124 template <class _CharT, class _Traits, class _RealType>
125 _LIBCPP_HIDE_FROM_ABI basic_ostream<_CharT, _Traits>&
126 operator<<(basic_ostream<_CharT, _Traits>& __os,
127 const exponential_distribution<_RealType>& __x)
128 {
129 __save_flags<_CharT, _Traits> __lx(__os);
130 typedef basic_ostream<_CharT, _Traits> _OStream;
131 __os.flags(_OStream::dec | _OStream::left | _OStream::fixed |
132 _OStream::scientific);
133 return __os << __x.lambda();
134 }
135
136 template <class _CharT, class _Traits, class _RealType>
137 _LIBCPP_HIDE_FROM_ABI basic_istream<_CharT, _Traits>&
138 operator>>(basic_istream<_CharT, _Traits>& __is,
139 exponential_distribution<_RealType>& __x)
140 {
141 typedef exponential_distribution<_RealType> _Eng;
142 typedef typename _Eng::result_type result_type;
143 typedef typename _Eng::param_type param_type;
144 __save_flags<_CharT, _Traits> __lx(__is);
145 typedef basic_istream<_CharT, _Traits> _Istream;
146 __is.flags(_Istream::dec | _Istream::skipws);
147 result_type __lambda;
148 __is >> __lambda;
149 if (!__is.fail())
150 __x.param(param_type(__lambda));
151 return __is;
152 }
153
154 _LIBCPP_END_NAMESPACE_STD
155
156 _LIBCPP_POP_MACROS
157
158 #endif // _LIBCPP___RANDOM_EXPONENTIAL_DISTRIBUTION_H
159