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___CXX03___RANDOM_EXPONENTIAL_DISTRIBUTION_H
10 #define _LIBCPP___CXX03___RANDOM_EXPONENTIAL_DISTRIBUTION_H
11
12 #include <__cxx03/__config>
13 #include <__cxx03/__random/generate_canonical.h>
14 #include <__cxx03/__random/is_valid.h>
15 #include <__cxx03/__random/uniform_real_distribution.h>
16 #include <__cxx03/cmath>
17 #include <__cxx03/iosfwd>
18 #include <__cxx03/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 <__cxx03/__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
__p_(param_type (__lambda))59 _LIBCPP_HIDE_FROM_ABI explicit exponential_distribution(result_type __lambda = 1) : __p_(param_type(__lambda)) {}
exponential_distribution(const param_type & __p)60 _LIBCPP_HIDE_FROM_ABI explicit exponential_distribution(const param_type& __p) : __p_(__p) {}
reset()61 _LIBCPP_HIDE_FROM_ABI void reset() {}
62
63 // generating functions
64 template <class _URNG>
operator()65 _LIBCPP_HIDE_FROM_ABI result_type operator()(_URNG& __g) {
66 return (*this)(__g, __p_);
67 }
68 template <class _URNG>
69 _LIBCPP_HIDE_FROM_ABI result_type operator()(_URNG& __g, const param_type& __p);
70
71 // property functions
lambda()72 _LIBCPP_HIDE_FROM_ABI result_type lambda() const { return __p_.lambda(); }
73
param()74 _LIBCPP_HIDE_FROM_ABI param_type param() const { return __p_; }
param(const param_type & __p)75 _LIBCPP_HIDE_FROM_ABI void param(const param_type& __p) { __p_ = __p; }
76
min()77 _LIBCPP_HIDE_FROM_ABI result_type min() const { return 0; }
max()78 _LIBCPP_HIDE_FROM_ABI result_type max() const { return numeric_limits<result_type>::infinity(); }
79
80 friend _LIBCPP_HIDE_FROM_ABI bool
81 operator==(const exponential_distribution& __x, const exponential_distribution& __y) {
82 return __x.__p_ == __y.__p_;
83 }
84 friend _LIBCPP_HIDE_FROM_ABI bool
85 operator!=(const exponential_distribution& __x, const exponential_distribution& __y) {
86 return !(__x == __y);
87 }
88 };
89
90 template <class _RealType>
91 template <class _URNG>
operator()92 _RealType exponential_distribution<_RealType>::operator()(_URNG& __g, const param_type& __p) {
93 static_assert(__libcpp_random_is_valid_urng<_URNG>::value, "");
94 return -std::log(result_type(1) - std::generate_canonical<result_type, numeric_limits<result_type>::digits>(__g)) /
95 __p.lambda();
96 }
97
98 template <class _CharT, class _Traits, class _RealType>
99 _LIBCPP_HIDE_FROM_ABI basic_ostream<_CharT, _Traits>&
100 operator<<(basic_ostream<_CharT, _Traits>& __os, const exponential_distribution<_RealType>& __x) {
101 __save_flags<_CharT, _Traits> __lx(__os);
102 typedef basic_ostream<_CharT, _Traits> _OStream;
103 __os.flags(_OStream::dec | _OStream::left | _OStream::fixed | _OStream::scientific);
104 return __os << __x.lambda();
105 }
106
107 template <class _CharT, class _Traits, class _RealType>
108 _LIBCPP_HIDE_FROM_ABI basic_istream<_CharT, _Traits>&
109 operator>>(basic_istream<_CharT, _Traits>& __is, exponential_distribution<_RealType>& __x) {
110 typedef exponential_distribution<_RealType> _Eng;
111 typedef typename _Eng::result_type result_type;
112 typedef typename _Eng::param_type param_type;
113 __save_flags<_CharT, _Traits> __lx(__is);
114 typedef basic_istream<_CharT, _Traits> _Istream;
115 __is.flags(_Istream::dec | _Istream::skipws);
116 result_type __lambda;
117 __is >> __lambda;
118 if (!__is.fail())
119 __x.param(param_type(__lambda));
120 return __is;
121 }
122
123 _LIBCPP_END_NAMESPACE_STD
124
125 _LIBCPP_POP_MACROS
126
127 #endif // _LIBCPP___CXX03___RANDOM_EXPONENTIAL_DISTRIBUTION_H
128