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