libcxx/include/__random/student_t_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_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
  43         explicit param_type(result_type __n = 1) : __n_(__n) {}
  44
  45         _LIBCPP_INLINE_VISIBILITY
  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
  64     student_t_distribution() : student_t_distribution(1) {}
  65     _LIBCPP_INLINE_VISIBILITY
  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
  74     explicit student_t_distribution(const param_type& __p)
  75         : __p_(__p) {}
  76     _LIBCPP_INLINE_VISIBILITY
  77     void reset() {__nd_.reset();}
  78
  79     // generating functions
  80     template<class _URNG>
  81         _LIBCPP_INLINE_VISIBILITY
  82         result_type operator()(_URNG& __g)
  83         {return (*this)(__g, __p_);}
  84     template<class _URNG>
  85     _LIBCPP_HIDE_FROM_ABI result_type operator()(_URNG& __g, const param_type& __p);
  86
  87     // property functions
  88     _LIBCPP_INLINE_VISIBILITY
  89     result_type n() const {return __p_.n();}
  90
  91     _LIBCPP_INLINE_VISIBILITY
  92     param_type param() const {return __p_;}
  93     _LIBCPP_INLINE_VISIBILITY
  94     void param(const param_type& __p) {__p_ = __p;}
  95
  96     _LIBCPP_INLINE_VISIBILITY
  97     result_type min() const {return -numeric_limits<result_type>::infinity();}
  98     _LIBCPP_INLINE_VISIBILITY
  99     result_type max() const {return numeric_limits<result_type>::infinity();}
 100
 101     friend _LIBCPP_INLINE_VISIBILITY
 102         bool operator==(const student_t_distribution& __x,
 103                         const student_t_distribution& __y)
 104         {return __x.__p_ == __y.__p_;}
 105     friend _LIBCPP_INLINE_VISIBILITY
 106         bool operator!=(const student_t_distribution& __x,
 107                         const student_t_distribution& __y)
 108         {return !(__x == __y);}
 109 };
 110
 111 template <class _RealType>
 112 template<class _URNG>
 113 _RealType
 114 student_t_distribution<_RealType>::operator()(_URNG& __g, const param_type& __p)
 115 {
 116     static_assert(__libcpp_random_is_valid_urng<_URNG>::value, "");
 117     gamma_distribution<result_type> __gd(__p.n() * .5, 2);
 118     return __nd_(__g) * _VSTD::sqrt(__p.n()/__gd(__g));
 119 }
 120
 121 template <class _CharT, class _Traits, class _RT>
 122 _LIBCPP_HIDE_FROM_ABI basic_ostream<_CharT, _Traits>&
 123 operator<<(basic_ostream<_CharT, _Traits>& __os,
 124            const student_t_distribution<_RT>& __x)
 125 {
 126     __save_flags<_CharT, _Traits> __lx(__os);
 127     typedef basic_ostream<_CharT, _Traits> _OStream;
 128     __os.flags(_OStream::dec | _OStream::left | _OStream::fixed |
 129                _OStream::scientific);
 130     __os << __x.n();
 131     return __os;
 132 }
 133
 134 template <class _CharT, class _Traits, class _RT>
 135 _LIBCPP_HIDE_FROM_ABI basic_istream<_CharT, _Traits>&
 136 operator>>(basic_istream<_CharT, _Traits>& __is,
 137            student_t_distribution<_RT>& __x)
 138 {
 139     typedef student_t_distribution<_RT> _Eng;
 140     typedef typename _Eng::result_type result_type;
 141     typedef typename _Eng::param_type param_type;
 142     __save_flags<_CharT, _Traits> __lx(__is);
 143     typedef basic_istream<_CharT, _Traits> _Istream;
 144     __is.flags(_Istream::dec | _Istream::skipws);
 145     result_type __n;
 146     __is >> __n;
 147     if (!__is.fail())
 148         __x.param(param_type(__n));
 149     return __is;
 150 }
 151
 152 _LIBCPP_END_NAMESPACE_STD
 153
 154 _LIBCPP_POP_MACROS
 155
 156 #endif // _LIBCPP___RANDOM_STUDENT_T_DISTRIBUTION_H