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
__lambda_(__lambda)44 _LIBCPP_HIDE_FROM_ABI explicit param_type(result_type __lambda = 1) : __lambda_(__lambda) {}
45
lambda()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
exponential_distribution()60 _LIBCPP_HIDE_FROM_ABI exponential_distribution() : exponential_distribution(1) {}
exponential_distribution(result_type __lambda)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
exponential_distribution(const param_type & __p)65 _LIBCPP_HIDE_FROM_ABI explicit exponential_distribution(const param_type& __p) : __p_(__p) {}
reset()66 _LIBCPP_HIDE_FROM_ABI void reset() {}
67
68 // generating functions
69 template <class _URNG>
operator()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
lambda()77 _LIBCPP_HIDE_FROM_ABI result_type lambda() const { return __p_.lambda(); }
78
param()79 _LIBCPP_HIDE_FROM_ABI param_type param() const { return __p_; }
param(const param_type & __p)80 _LIBCPP_HIDE_FROM_ABI void param(const param_type& __p) { __p_ = __p; }
81
min()82 _LIBCPP_HIDE_FROM_ABI result_type min() const { return 0; }
max()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>
operator()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