libcxx/include/__random/cauchy_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_CAUCHY_DISTRIBUTION_H
  10 #define _LIBCPP___RANDOM_CAUCHY_DISTRIBUTION_H
  11
  12 #include <__config>
  13 #include <__random/is_valid.h>
  14 #include <__random/uniform_real_distribution.h>
  15 #include <cmath>
  16 #include <iosfwd>
  17 #include <limits>
  18
  19 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  20 #  pragma GCC system_header
  21 #endif
  22
  23 _LIBCPP_PUSH_MACROS
  24 #include <__undef_macros>
  25
  26 _LIBCPP_BEGIN_NAMESPACE_STD
  27
  28 template<class _RealType = double>
  29 class _LIBCPP_TEMPLATE_VIS cauchy_distribution
  30 {
  31 public:
  32     // types
  33     typedef _RealType result_type;
  34
  35     class _LIBCPP_TEMPLATE_VIS param_type
  36     {
  37         result_type __a_;
  38         result_type __b_;
  39     public:
  40         typedef cauchy_distribution distribution_type;
  41
  42         _LIBCPP_INLINE_VISIBILITY
  43         explicit param_type(result_type __a = 0, result_type __b = 1)
  44             : __a_(__a), __b_(__b) {}
  45
  46         _LIBCPP_INLINE_VISIBILITY
  47         result_type a() const {return __a_;}
  48         _LIBCPP_INLINE_VISIBILITY
  49         result_type b() const {return __b_;}
  50
  51         friend _LIBCPP_INLINE_VISIBILITY
  52             bool operator==(const param_type& __x, const param_type& __y)
  53             {return __x.__a_ == __y.__a_ && __x.__b_ == __y.__b_;}
  54         friend _LIBCPP_INLINE_VISIBILITY
  55             bool operator!=(const param_type& __x, const param_type& __y)
  56             {return !(__x == __y);}
  57     };
  58
  59 private:
  60     param_type __p_;
  61
  62 public:
  63     // constructor and reset functions
  64 #ifndef _LIBCPP_CXX03_LANG
  65     _LIBCPP_INLINE_VISIBILITY
  66     cauchy_distribution() : cauchy_distribution(0) {}
  67     _LIBCPP_INLINE_VISIBILITY
  68     explicit cauchy_distribution(result_type __a, result_type __b = 1)
  69         : __p_(param_type(__a, __b)) {}
  70 #else
  71     _LIBCPP_INLINE_VISIBILITY
  72     explicit cauchy_distribution(result_type __a = 0, result_type __b = 1)
  73         : __p_(param_type(__a, __b)) {}
  74 #endif
  75     _LIBCPP_INLINE_VISIBILITY
  76     explicit cauchy_distribution(const param_type& __p)
  77         : __p_(__p) {}
  78     _LIBCPP_INLINE_VISIBILITY
  79     void reset() {}
  80
  81     // generating functions
  82     template<class _URNG>
  83         _LIBCPP_INLINE_VISIBILITY
  84         result_type operator()(_URNG& __g)
  85         {return (*this)(__g, __p_);}
  86     template<class _URNG> _LIBCPP_INLINE_VISIBILITY result_type operator()(_URNG& __g, const param_type& __p);
  87
  88     // property functions
  89     _LIBCPP_INLINE_VISIBILITY
  90     result_type a() const {return __p_.a();}
  91     _LIBCPP_INLINE_VISIBILITY
  92     result_type b() const {return __p_.b();}
  93
  94     _LIBCPP_INLINE_VISIBILITY
  95     param_type param() const {return __p_;}
  96     _LIBCPP_INLINE_VISIBILITY
  97     void param(const param_type& __p) {__p_ = __p;}
  98
  99     _LIBCPP_INLINE_VISIBILITY
 100     result_type min() const {return -numeric_limits<result_type>::infinity();}
 101     _LIBCPP_INLINE_VISIBILITY
 102     result_type max() const {return numeric_limits<result_type>::infinity();}
 103
 104     friend _LIBCPP_INLINE_VISIBILITY
 105         bool operator==(const cauchy_distribution& __x,
 106                         const cauchy_distribution& __y)
 107         {return __x.__p_ == __y.__p_;}
 108     friend _LIBCPP_INLINE_VISIBILITY
 109         bool operator!=(const cauchy_distribution& __x,
 110                         const cauchy_distribution& __y)
 111         {return !(__x == __y);}
 112 };
 113
 114 template <class _RealType>
 115 template<class _URNG>
 116 inline
 117 _RealType
 118 cauchy_distribution<_RealType>::operator()(_URNG& __g, const param_type& __p)
 119 {
 120     static_assert(__libcpp_random_is_valid_urng<_URNG>::value, "");
 121     uniform_real_distribution<result_type> __gen;
 122     // purposefully let tan arg get as close to pi/2 as it wants, tan will return a finite
 123     return __p.a() + __p.b() * _VSTD::tan(3.1415926535897932384626433832795 * __gen(__g));
 124 }
 125
 126 template <class _CharT, class _Traits, class _RT>
 127 _LIBCPP_HIDE_FROM_ABI basic_ostream<_CharT, _Traits>&
 128 operator<<(basic_ostream<_CharT, _Traits>& __os,
 129            const cauchy_distribution<_RT>& __x)
 130 {
 131     __save_flags<_CharT, _Traits> __lx(__os);
 132     typedef basic_ostream<_CharT, _Traits> _OStream;
 133     __os.flags(_OStream::dec | _OStream::left | _OStream::fixed |
 134                _OStream::scientific);
 135     _CharT __sp = __os.widen(' ');
 136     __os.fill(__sp);
 137     __os << __x.a() << __sp << __x.b();
 138     return __os;
 139 }
 140
 141 template <class _CharT, class _Traits, class _RT>
 142 _LIBCPP_HIDE_FROM_ABI basic_istream<_CharT, _Traits>&
 143 operator>>(basic_istream<_CharT, _Traits>& __is,
 144            cauchy_distribution<_RT>& __x)
 145 {
 146     typedef cauchy_distribution<_RT> _Eng;
 147     typedef typename _Eng::result_type result_type;
 148     typedef typename _Eng::param_type param_type;
 149     __save_flags<_CharT, _Traits> __lx(__is);
 150     typedef basic_istream<_CharT, _Traits> _Istream;
 151     __is.flags(_Istream::dec | _Istream::skipws);
 152     result_type __a;
 153     result_type __b;
 154     __is >> __a >> __b;
 155     if (!__is.fail())
 156         __x.param(param_type(__a, __b));
 157     return __is;
 158 }
 159
 160 _LIBCPP_END_NAMESPACE_STD
 161
 162 _LIBCPP_POP_MACROS
 163
 164 #endif // _LIBCPP___RANDOM_CAUCHY_DISTRIBUTION_H