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_CHI_SQUARED_DISTRIBUTION_H
10#define _LIBCPP___RANDOM_CHI_SQUARED_DISTRIBUTION_H
11
12#include <__config>
13#include <__random/gamma_distribution.h>
14#include <__random/is_valid.h>
15#include <iosfwd>
16#include <limits>
17
18#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
19# pragma GCC system_header
20#endif
21
22_LIBCPP_PUSH_MACROS
23#include <__undef_macros>
24
25_LIBCPP_BEGIN_NAMESPACE_STD
26
27template <class _RealType = double>
28class chi_squared_distribution {
29 static_assert(__libcpp_random_is_valid_realtype<_RealType>::value,
30 "RealType must be a supported floating-point type");
31
32public:
33 // types
34 typedef _RealType result_type;
35
36 class param_type {
37 result_type __n_;
38
39 public:
40 typedef chi_squared_distribution distribution_type;
41
42 _LIBCPP_HIDE_FROM_ABI explicit param_type(result_type __n = 1) : __n_(__n) {}
43
44 _LIBCPP_HIDE_FROM_ABI result_type n() const { return __n_; }
45
46 friend _LIBCPP_HIDE_FROM_ABI bool operator==(const param_type& __x, const param_type& __y) {
47 return __x.__n_ == __y.__n_;
48 }
49 friend _LIBCPP_HIDE_FROM_ABI bool operator!=(const param_type& __x, const param_type& __y) { return !(__x == __y); }
50 };
51
52private:
53 param_type __p_;
54
55public:
56 // constructor and reset functions
57#ifndef _LIBCPP_CXX03_LANG
58 _LIBCPP_HIDE_FROM_ABI chi_squared_distribution() : chi_squared_distribution(1) {}
59 _LIBCPP_HIDE_FROM_ABI explicit chi_squared_distribution(result_type __n) : __p_(param_type(__n)) {}
60#else
61 _LIBCPP_HIDE_FROM_ABI explicit chi_squared_distribution(result_type __n = 1) : __p_(param_type(__n)) {}
62#endif
63 _LIBCPP_HIDE_FROM_ABI explicit chi_squared_distribution(const param_type& __p) : __p_(__p) {}
64 _LIBCPP_HIDE_FROM_ABI void reset() {}
65
66 // generating functions
67 template <class _URNG>
68 _LIBCPP_HIDE_FROM_ABI result_type operator()(_URNG& __g) {
69 return (*this)(__g, __p_);
70 }
71 template <class _URNG>
72 _LIBCPP_HIDE_FROM_ABI result_type operator()(_URNG& __g, const param_type& __p) {
73 return gamma_distribution<result_type>(__p.n() / 2, 2)(__g);
74 }
75
76 // property functions
77 _LIBCPP_HIDE_FROM_ABI result_type n() const { return __p_.n(); }
78
79 _LIBCPP_HIDE_FROM_ABI param_type param() const { return __p_; }
80 _LIBCPP_HIDE_FROM_ABI void param(const param_type& __p) { __p_ = __p; }
81
82 _LIBCPP_HIDE_FROM_ABI result_type min() const { return 0; }
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 chi_squared_distribution& __x, const chi_squared_distribution& __y) {
87 return __x.__p_ == __y.__p_;
88 }
89 friend _LIBCPP_HIDE_FROM_ABI bool
90 operator!=(const chi_squared_distribution& __x, const chi_squared_distribution& __y) {
91 return !(__x == __y);
92 }
93};
94
95template <class _CharT, class _Traits, class _RT>
96_LIBCPP_HIDE_FROM_ABI basic_ostream<_CharT, _Traits>&
97operator<<(basic_ostream<_CharT, _Traits>& __os, const chi_squared_distribution<_RT>& __x) {
98 __save_flags<_CharT, _Traits> __lx(__os);
99 typedef basic_ostream<_CharT, _Traits> _OStream;
100 __os.flags(_OStream::dec | _OStream::left | _OStream::fixed | _OStream::scientific);
101 __os << __x.n();
102 return __os;
103}
104
105template <class _CharT, class _Traits, class _RT>
106_LIBCPP_HIDE_FROM_ABI basic_istream<_CharT, _Traits>&
107operator>>(basic_istream<_CharT, _Traits>& __is, chi_squared_distribution<_RT>& __x) {
108 typedef chi_squared_distribution<_RT> _Eng;
109 typedef typename _Eng::result_type result_type;
110 typedef typename _Eng::param_type param_type;
111 __save_flags<_CharT, _Traits> __lx(__is);
112 typedef basic_istream<_CharT, _Traits> _Istream;
113 __is.flags(_Istream::dec | _Istream::skipws);
114 result_type __n;
115 __is >> __n;
116 if (!__is.fail())
117 __x.param(param_type(__n));
118 return __is;
119}
120
121_LIBCPP_END_NAMESPACE_STD
122
123_LIBCPP_POP_MACROS
124
125#endif // _LIBCPP___RANDOM_CHI_SQUARED_DISTRIBUTION_H
126