v1/__random/cauchy_distribution.h

0001 //===----------------------------------------------------------------------===//
0002 //
0003 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
0004 // See https://llvm.org/LICENSE.txt for license information.
0005 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
0006 //
0007 //===----------------------------------------------------------------------===//
0008
0009 #ifndef _LIBCPP___RANDOM_CAUCHY_DISTRIBUTION_H
0010 #define _LIBCPP___RANDOM_CAUCHY_DISTRIBUTION_H
0011
0012 #include <__config>
0013 #include <__random/is_valid.h>
0014 #include <__random/uniform_real_distribution.h>
0015 #include <cmath>
0016 #include <iosfwd>
0017 #include <limits>
0018
0019 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
0020 #  pragma GCC system_header
0021 #endif
0022
0023 _LIBCPP_PUSH_MACROS
0024 #include <__undef_macros>
0025
0026 _LIBCPP_BEGIN_NAMESPACE_STD
0027
0028 template <class _RealType = double>
0029 class _LIBCPP_TEMPLATE_VIS cauchy_distribution {
0030   static_assert(__libcpp_random_is_valid_realtype<_RealType>::value,
0031                 "RealType must be a supported floating-point type");
0032
0033 public:
0034   // types
0035   typedef _RealType result_type;
0036
0037   class _LIBCPP_TEMPLATE_VIS param_type {
0038     result_type __a_;
0039     result_type __b_;
0040
0041   public:
0042     typedef cauchy_distribution distribution_type;
0043
0044     _LIBCPP_HIDE_FROM_ABI explicit param_type(result_type __a = 0, result_type __b = 1) : __a_(__a), __b_(__b) {}
0045
0046     _LIBCPP_HIDE_FROM_ABI result_type a() const { return __a_; }
0047     _LIBCPP_HIDE_FROM_ABI result_type b() const { return __b_; }
0048
0049     friend _LIBCPP_HIDE_FROM_ABI bool operator==(const param_type& __x, const param_type& __y) {
0050       return __x.__a_ == __y.__a_ && __x.__b_ == __y.__b_;
0051     }
0052     friend _LIBCPP_HIDE_FROM_ABI bool operator!=(const param_type& __x, const param_type& __y) { return !(__x == __y); }
0053   };
0054
0055 private:
0056   param_type __p_;
0057
0058 public:
0059   // constructor and reset functions
0060 #ifndef _LIBCPP_CXX03_LANG
0061   _LIBCPP_HIDE_FROM_ABI cauchy_distribution() : cauchy_distribution(0) {}
0062   _LIBCPP_HIDE_FROM_ABI explicit cauchy_distribution(result_type __a, result_type __b = 1)
0063       : __p_(param_type(__a, __b)) {}
0064 #else
0065   _LIBCPP_HIDE_FROM_ABI explicit cauchy_distribution(result_type __a = 0, result_type __b = 1)
0066       : __p_(param_type(__a, __b)) {}
0067 #endif
0068   _LIBCPP_HIDE_FROM_ABI explicit cauchy_distribution(const param_type& __p) : __p_(__p) {}
0069   _LIBCPP_HIDE_FROM_ABI void reset() {}
0070
0071   // generating functions
0072   template <class _URNG>
0073   _LIBCPP_HIDE_FROM_ABI result_type operator()(_URNG& __g) {
0074     return (*this)(__g, __p_);
0075   }
0076   template <class _URNG>
0077   _LIBCPP_HIDE_FROM_ABI result_type operator()(_URNG& __g, const param_type& __p);
0078
0079   // property functions
0080   _LIBCPP_HIDE_FROM_ABI result_type a() const { return __p_.a(); }
0081   _LIBCPP_HIDE_FROM_ABI result_type b() const { return __p_.b(); }
0082
0083   _LIBCPP_HIDE_FROM_ABI param_type param() const { return __p_; }
0084   _LIBCPP_HIDE_FROM_ABI void param(const param_type& __p) { __p_ = __p; }
0085
0086   _LIBCPP_HIDE_FROM_ABI result_type min() const { return -numeric_limits<result_type>::infinity(); }
0087   _LIBCPP_HIDE_FROM_ABI result_type max() const { return numeric_limits<result_type>::infinity(); }
0088
0089   friend _LIBCPP_HIDE_FROM_ABI bool operator==(const cauchy_distribution& __x, const cauchy_distribution& __y) {
0090     return __x.__p_ == __y.__p_;
0091   }
0092   friend _LIBCPP_HIDE_FROM_ABI bool operator!=(const cauchy_distribution& __x, const cauchy_distribution& __y) {
0093     return !(__x == __y);
0094   }
0095 };
0096
0097 template <class _RealType>
0098 template <class _URNG>
0099 inline _RealType cauchy_distribution<_RealType>::operator()(_URNG& __g, const param_type& __p) {
0100   static_assert(__libcpp_random_is_valid_urng<_URNG>::value, "");
0101   uniform_real_distribution<result_type> __gen;
0102   // purposefully let tan arg get as close to pi/2 as it wants, tan will return a finite
0103   return __p.a() + __p.b() * std::tan(3.1415926535897932384626433832795 * __gen(__g));
0104 }
0105
0106 template <class _CharT, class _Traits, class _RT>
0107 _LIBCPP_HIDE_FROM_ABI basic_ostream<_CharT, _Traits>&
0108 operator<<(basic_ostream<_CharT, _Traits>& __os, const cauchy_distribution<_RT>& __x) {
0109   __save_flags<_CharT, _Traits> __lx(__os);
0110   typedef basic_ostream<_CharT, _Traits> _OStream;
0111   __os.flags(_OStream::dec | _OStream::left | _OStream::fixed | _OStream::scientific);
0112   _CharT __sp = __os.widen(' ');
0113   __os.fill(__sp);
0114   __os << __x.a() << __sp << __x.b();
0115   return __os;
0116 }
0117
0118 template <class _CharT, class _Traits, class _RT>
0119 _LIBCPP_HIDE_FROM_ABI basic_istream<_CharT, _Traits>&
0120 operator>>(basic_istream<_CharT, _Traits>& __is, cauchy_distribution<_RT>& __x) {
0121   typedef cauchy_distribution<_RT> _Eng;
0122   typedef typename _Eng::result_type result_type;
0123   typedef typename _Eng::param_type param_type;
0124   __save_flags<_CharT, _Traits> __lx(__is);
0125   typedef basic_istream<_CharT, _Traits> _Istream;
0126   __is.flags(_Istream::dec | _Istream::skipws);
0127   result_type __a;
0128   result_type __b;
0129   __is >> __a >> __b;
0130   if (!__is.fail())
0131     __x.param(param_type(__a, __b));
0132   return __is;
0133 }
0134
0135 _LIBCPP_END_NAMESPACE_STD
0136
0137 _LIBCPP_POP_MACROS
0138
0139 #endif // _LIBCPP___RANDOM_CAUCHY_DISTRIBUTION_H