libcxx/include/__random/chi_squared_distribution.h

   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 <iosfwd>
  15 #include <limits>
  16
  17 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  18 #  pragma GCC system_header
  19 #endif
  20
  21 _LIBCPP_PUSH_MACROS
  22 #include <__undef_macros>
  23
  24 _LIBCPP_BEGIN_NAMESPACE_STD
  25
  26 template<class _RealType = double>
  27 class _LIBCPP_TEMPLATE_VIS chi_squared_distribution
  28 {
  29 public:
  30     // types
  31     typedef _RealType result_type;
  32
  33     class _LIBCPP_TEMPLATE_VIS param_type
  34     {
  35         result_type __n_;
  36     public:
  37         typedef chi_squared_distribution distribution_type;
  38
  39         _LIBCPP_INLINE_VISIBILITY
  40         explicit param_type(result_type __n = 1) : __n_(__n) {}
  41
  42         _LIBCPP_INLINE_VISIBILITY
  43         result_type n() const {return __n_;}
  44
  45         friend _LIBCPP_INLINE_VISIBILITY
  46             bool operator==(const param_type& __x, const param_type& __y)
  47             {return __x.__n_ == __y.__n_;}
  48         friend _LIBCPP_INLINE_VISIBILITY
  49             bool operator!=(const param_type& __x, const param_type& __y)
  50             {return !(__x == __y);}
  51     };
  52
  53 private:
  54     param_type __p_;
  55
  56 public:
  57     // constructor and reset functions
  58 #ifndef _LIBCPP_CXX03_LANG
  59     _LIBCPP_INLINE_VISIBILITY
  60     chi_squared_distribution() : chi_squared_distribution(1) {}
  61     _LIBCPP_INLINE_VISIBILITY
  62     explicit chi_squared_distribution(result_type __n)
  63         : __p_(param_type(__n)) {}
  64 #else
  65     _LIBCPP_INLINE_VISIBILITY
  66     explicit chi_squared_distribution(result_type __n = 1)
  67         : __p_(param_type(__n)) {}
  68 #endif
  69     _LIBCPP_INLINE_VISIBILITY
  70     explicit chi_squared_distribution(const param_type& __p)
  71         : __p_(__p) {}
  72     _LIBCPP_INLINE_VISIBILITY
  73     void reset() {}
  74
  75     // generating functions
  76     template<class _URNG>
  77         _LIBCPP_INLINE_VISIBILITY
  78         result_type operator()(_URNG& __g)
  79         {return (*this)(__g, __p_);}
  80     template<class _URNG>
  81         _LIBCPP_INLINE_VISIBILITY
  82         result_type operator()(_URNG& __g, const param_type& __p)
  83         {return gamma_distribution<result_type>(__p.n() / 2, 2)(__g);}
  84
  85     // property functions
  86     _LIBCPP_INLINE_VISIBILITY
  87     result_type n() const {return __p_.n();}
  88
  89     _LIBCPP_INLINE_VISIBILITY
  90     param_type param() const {return __p_;}
  91     _LIBCPP_INLINE_VISIBILITY
  92     void param(const param_type& __p) {__p_ = __p;}
  93
  94     _LIBCPP_INLINE_VISIBILITY
  95     result_type min() const {return 0;}
  96     _LIBCPP_INLINE_VISIBILITY
  97     result_type max() const {return numeric_limits<result_type>::infinity();}
  98
  99     friend _LIBCPP_INLINE_VISIBILITY
 100         bool operator==(const chi_squared_distribution& __x,
 101                         const chi_squared_distribution& __y)
 102         {return __x.__p_ == __y.__p_;}
 103     friend _LIBCPP_INLINE_VISIBILITY
 104         bool operator!=(const chi_squared_distribution& __x,
 105                         const chi_squared_distribution& __y)
 106         {return !(__x == __y);}
 107 };
 108
 109 template <class _CharT, class _Traits, class _RT>
 110 _LIBCPP_HIDE_FROM_ABI basic_ostream<_CharT, _Traits>&
 111 operator<<(basic_ostream<_CharT, _Traits>& __os,
 112            const chi_squared_distribution<_RT>& __x)
 113 {
 114     __save_flags<_CharT, _Traits> __lx(__os);
 115     typedef basic_ostream<_CharT, _Traits> _OStream;
 116     __os.flags(_OStream::dec | _OStream::left | _OStream::fixed |
 117                _OStream::scientific);
 118     __os << __x.n();
 119     return __os;
 120 }
 121
 122 template <class _CharT, class _Traits, class _RT>
 123 _LIBCPP_HIDE_FROM_ABI basic_istream<_CharT, _Traits>&
 124 operator>>(basic_istream<_CharT, _Traits>& __is,
 125            chi_squared_distribution<_RT>& __x)
 126 {
 127     typedef chi_squared_distribution<_RT> _Eng;
 128     typedef typename _Eng::result_type result_type;
 129     typedef typename _Eng::param_type param_type;
 130     __save_flags<_CharT, _Traits> __lx(__is);
 131     typedef basic_istream<_CharT, _Traits> _Istream;
 132     __is.flags(_Istream::dec | _Istream::skipws);
 133     result_type __n;
 134     __is >> __n;
 135     if (!__is.fail())
 136         __x.param(param_type(__n));
 137     return __is;
 138 }
 139
 140 _LIBCPP_END_NAMESPACE_STD
 141
 142 _LIBCPP_POP_MACROS
 143
 144 #endif // _LIBCPP___RANDOM_CHI_SQUARED_DISTRIBUTION_H