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   static_assert(__libcpp_random_is_valid_realtype<_RealType>::value,
  32                 "RealType must be a supported floating-point type");
  33
  34 public:
  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
  54 private:
  55   param_type __p_;
  56   normal_distribution<result_type> __nd_;
  57
  58 public:
  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
  94 template <class _RealType>
  95 template <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
 102 template <class _CharT, class _Traits, class _RT>
 103 _LIBCPP_HIDE_FROM_ABI basic_ostream<_CharT, _Traits>&
 104 operator<<(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
 112 template <class _CharT, class _Traits, class _RT>
 113 _LIBCPP_HIDE_FROM_ABI basic_istream<_CharT, _Traits>&
 114 operator>>(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