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
29template <class _RealType = double>
30class _LIBCPP_TEMPLATE_VIS student_t_distribution {
31  static_assert(__libcpp_random_is_valid_realtype<_RealType>::value,
32                "RealType must be a supported floating-point type");
33
34public:
35  // types
36  typedef _RealType result_type;
37
38  class _LIBCPP_TEMPLATE_VIS param_type {
39    result_type __n_;
40
41  public:
42    typedef student_t_distribution distribution_type;
43
44    _LIBCPP_HIDE_FROM_ABI explicit param_type(result_type __n = 1) : __n_(__n) {}
45
46    _LIBCPP_HIDE_FROM_ABI result_type n() const { return __n_; }
47
48    friend _LIBCPP_HIDE_FROM_ABI bool operator==(const param_type& __x, const param_type& __y) {
49      return __x.__n_ == __y.__n_;
50    }
51    friend _LIBCPP_HIDE_FROM_ABI bool operator!=(const param_type& __x, const param_type& __y) { return !(__x == __y); }
52  };
53
54private:
55  param_type __p_;
56  normal_distribution<result_type> __nd_;
57
58public:
59  // constructor and reset functions
60#ifndef _LIBCPP_CXX03_LANG
61  _LIBCPP_HIDE_FROM_ABI student_t_distribution() : student_t_distribution(1) {}
62  _LIBCPP_HIDE_FROM_ABI explicit student_t_distribution(result_type __n) : __p_(param_type(__n)) {}
63#else
64  _LIBCPP_HIDE_FROM_ABI explicit student_t_distribution(result_type __n = 1) : __p_(param_type(__n)) {}
65#endif
66  _LIBCPP_HIDE_FROM_ABI explicit student_t_distribution(const param_type& __p) : __p_(__p) {}
67  _LIBCPP_HIDE_FROM_ABI void reset() { __nd_.reset(); }
68
69  // generating functions
70  template <class _URNG>
71  _LIBCPP_HIDE_FROM_ABI result_type operator()(_URNG& __g) {
72    return (*this)(__g, __p_);
73  }
74  template <class _URNG>
75  _LIBCPP_HIDE_FROM_ABI result_type operator()(_URNG& __g, const param_type& __p);
76
77  // property functions
78  _LIBCPP_HIDE_FROM_ABI result_type n() const { return __p_.n(); }
79
80  _LIBCPP_HIDE_FROM_ABI param_type param() const { return __p_; }
81  _LIBCPP_HIDE_FROM_ABI void param(const param_type& __p) { __p_ = __p; }
82
83  _LIBCPP_HIDE_FROM_ABI result_type min() const { return -numeric_limits<result_type>::infinity(); }
84  _LIBCPP_HIDE_FROM_ABI result_type max() const { return numeric_limits<result_type>::infinity(); }
85
86  friend _LIBCPP_HIDE_FROM_ABI bool operator==(const student_t_distribution& __x, const student_t_distribution& __y) {
87    return __x.__p_ == __y.__p_;
88  }
89  friend _LIBCPP_HIDE_FROM_ABI bool operator!=(const student_t_distribution& __x, const student_t_distribution& __y) {
90    return !(__x == __y);
91  }
92};
93
94template <class _RealType>
95template <class _URNG>
96_RealType student_t_distribution<_RealType>::operator()(_URNG& __g, const param_type& __p) {
97  static_assert(__libcpp_random_is_valid_urng<_URNG>::value, "");
98  gamma_distribution<result_type> __gd(__p.n() * .5, 2);
99  return __nd_(__g) * std::sqrt(__p.n() / __gd(__g));
100}
101
102template <class _CharT, class _Traits, class _RT>
103_LIBCPP_HIDE_FROM_ABI basic_ostream<_CharT, _Traits>&
104operator<<(basic_ostream<_CharT, _Traits>& __os, const student_t_distribution<_RT>& __x) {
105  __save_flags<_CharT, _Traits> __lx(__os);
106  typedef basic_ostream<_CharT, _Traits> _OStream;
107  __os.flags(_OStream::dec | _OStream::left | _OStream::fixed | _OStream::scientific);
108  __os << __x.n();
109  return __os;
110}
111
112template <class _CharT, class _Traits, class _RT>
113_LIBCPP_HIDE_FROM_ABI basic_istream<_CharT, _Traits>&
114operator>>(basic_istream<_CharT, _Traits>& __is, student_t_distribution<_RT>& __x) {
115  typedef student_t_distribution<_RT> _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 __n;
122  __is >> __n;
123  if (!__is.fail())
124    __x.param(param_type(__n));
125  return __is;
126}
127
128_LIBCPP_END_NAMESPACE_STD
129
130_LIBCPP_POP_MACROS
131
132#endif // _LIBCPP___RANDOM_STUDENT_T_DISTRIBUTION_H
133