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 <__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
  27 template <class _RealType = double>
  28 class _LIBCPP_TEMPLATE_VIS chi_squared_distribution {
  29   static_assert(__libcpp_random_is_valid_realtype<_RealType>::value,
  30                 "RealType must be a supported floating-point type");
  31
  32 public:
  33   // types
  34   typedef _RealType result_type;
  35
  36   class _LIBCPP_TEMPLATE_VIS 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
  52 private:
  53   param_type __p_;
  54
  55 public:
  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
  95 template <class _CharT, class _Traits, class _RT>
  96 _LIBCPP_HIDE_FROM_ABI basic_ostream<_CharT, _Traits>&
  97 operator<<(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
 105 template <class _CharT, class _Traits, class _RT>
 106 _LIBCPP_HIDE_FROM_ABI basic_istream<_CharT, _Traits>&
 107 operator>>(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