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_STUDENT_T_DISTRIBUTION_H
10 #define _LIBCPP___RANDOM_STUDENT_T_DISTRIBUTION_H
11
12 #include <__config>
13 #include <__random/gamma_distribution.h>
14 #include <__random/is_valid.h>
15 #include <__random/normal_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 student_t_distribution
31 {
32 public:
33 // types
34 typedef _RealType result_type;
35
36 class _LIBCPP_TEMPLATE_VIS param_type
37 {
38 result_type __n_;
39 public:
40 typedef student_t_distribution distribution_type;
41
42 _LIBCPP_INLINE_VISIBILITY
__n_(__n)43 explicit param_type(result_type __n = 1) : __n_(__n) {}
44
45 _LIBCPP_INLINE_VISIBILITY
n()46 result_type n() const {return __n_;}
47
48 friend _LIBCPP_INLINE_VISIBILITY
49 bool operator==(const param_type& __x, const param_type& __y)
50 {return __x.__n_ == __y.__n_;}
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 normal_distribution<result_type> __nd_;
59
60 public:
61 // constructor and reset functions
62 #ifndef _LIBCPP_CXX03_LANG
63 _LIBCPP_INLINE_VISIBILITY
student_t_distribution()64 student_t_distribution() : student_t_distribution(1) {}
65 _LIBCPP_INLINE_VISIBILITY
student_t_distribution(result_type __n)66 explicit student_t_distribution(result_type __n)
67 : __p_(param_type(__n)) {}
68 #else
69 _LIBCPP_INLINE_VISIBILITY
70 explicit student_t_distribution(result_type __n = 1)
71 : __p_(param_type(__n)) {}
72 #endif
73 _LIBCPP_INLINE_VISIBILITY
student_t_distribution(const param_type & __p)74 explicit student_t_distribution(const param_type& __p)
75 : __p_(__p) {}
76 _LIBCPP_INLINE_VISIBILITY
reset()77 void reset() {__nd_.reset();}
78
79 // generating functions
80 template<class _URNG>
81 _LIBCPP_INLINE_VISIBILITY
operator()82 result_type operator()(_URNG& __g)
83 {return (*this)(__g, __p_);}
84 template<class _URNG> result_type operator()(_URNG& __g, const param_type& __p);
85
86 // property functions
87 _LIBCPP_INLINE_VISIBILITY
n()88 result_type n() const {return __p_.n();}
89
90 _LIBCPP_INLINE_VISIBILITY
param()91 param_type param() const {return __p_;}
92 _LIBCPP_INLINE_VISIBILITY
param(const param_type & __p)93 void param(const param_type& __p) {__p_ = __p;}
94
95 _LIBCPP_INLINE_VISIBILITY
min()96 result_type min() const {return -numeric_limits<result_type>::infinity();}
97 _LIBCPP_INLINE_VISIBILITY
max()98 result_type max() const {return numeric_limits<result_type>::infinity();}
99
100 friend _LIBCPP_INLINE_VISIBILITY
101 bool operator==(const student_t_distribution& __x,
102 const student_t_distribution& __y)
103 {return __x.__p_ == __y.__p_;}
104 friend _LIBCPP_INLINE_VISIBILITY
105 bool operator!=(const student_t_distribution& __x,
106 const student_t_distribution& __y)
107 {return !(__x == __y);}
108 };
109
110 template <class _RealType>
111 template<class _URNG>
112 _RealType
operator()113 student_t_distribution<_RealType>::operator()(_URNG& __g, const param_type& __p)
114 {
115 static_assert(__libcpp_random_is_valid_urng<_URNG>::value, "");
116 gamma_distribution<result_type> __gd(__p.n() * .5, 2);
117 return __nd_(__g) * _VSTD::sqrt(__p.n()/__gd(__g));
118 }
119
120 template <class _CharT, class _Traits, class _RT>
121 _LIBCPP_HIDE_FROM_ABI basic_ostream<_CharT, _Traits>&
122 operator<<(basic_ostream<_CharT, _Traits>& __os,
123 const student_t_distribution<_RT>& __x)
124 {
125 __save_flags<_CharT, _Traits> __lx(__os);
126 typedef basic_ostream<_CharT, _Traits> _OStream;
127 __os.flags(_OStream::dec | _OStream::left | _OStream::fixed |
128 _OStream::scientific);
129 __os << __x.n();
130 return __os;
131 }
132
133 template <class _CharT, class _Traits, class _RT>
134 _LIBCPP_HIDE_FROM_ABI basic_istream<_CharT, _Traits>&
135 operator>>(basic_istream<_CharT, _Traits>& __is,
136 student_t_distribution<_RT>& __x)
137 {
138 typedef student_t_distribution<_RT> _Eng;
139 typedef typename _Eng::result_type result_type;
140 typedef typename _Eng::param_type param_type;
141 __save_flags<_CharT, _Traits> __lx(__is);
142 typedef basic_istream<_CharT, _Traits> _Istream;
143 __is.flags(_Istream::dec | _Istream::skipws);
144 result_type __n;
145 __is >> __n;
146 if (!__is.fail())
147 __x.param(param_type(__n));
148 return __is;
149 }
150
151 _LIBCPP_END_NAMESPACE_STD
152
153 _LIBCPP_POP_MACROS
154
155 #endif // _LIBCPP___RANDOM_STUDENT_T_DISTRIBUTION_H
156