xref: /freebsd-src/contrib/llvm-project/libcxx/include/__random/exponential_distribution.h (revision cb14a3fe5122c879eae1fb480ed7ce82a699ddb6)
14824e7fdSDimitry Andric //===----------------------------------------------------------------------===//
24824e7fdSDimitry Andric //
34824e7fdSDimitry Andric // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
44824e7fdSDimitry Andric // See https://llvm.org/LICENSE.txt for license information.
54824e7fdSDimitry Andric // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
64824e7fdSDimitry Andric //
74824e7fdSDimitry Andric //===----------------------------------------------------------------------===//
84824e7fdSDimitry Andric 
94824e7fdSDimitry Andric #ifndef _LIBCPP___RANDOM_EXPONENTIAL_DISTRIBUTION_H
104824e7fdSDimitry Andric #define _LIBCPP___RANDOM_EXPONENTIAL_DISTRIBUTION_H
114824e7fdSDimitry Andric 
124824e7fdSDimitry Andric #include <__config>
134824e7fdSDimitry Andric #include <__random/generate_canonical.h>
1481ad6265SDimitry Andric #include <__random/is_valid.h>
154824e7fdSDimitry Andric #include <__random/uniform_real_distribution.h>
164824e7fdSDimitry Andric #include <cmath>
174824e7fdSDimitry Andric #include <iosfwd>
184824e7fdSDimitry Andric #include <limits>
194824e7fdSDimitry Andric 
204824e7fdSDimitry Andric #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
214824e7fdSDimitry Andric #  pragma GCC system_header
224824e7fdSDimitry Andric #endif
234824e7fdSDimitry Andric 
244824e7fdSDimitry Andric _LIBCPP_PUSH_MACROS
254824e7fdSDimitry Andric #include <__undef_macros>
264824e7fdSDimitry Andric 
274824e7fdSDimitry Andric _LIBCPP_BEGIN_NAMESPACE_STD
284824e7fdSDimitry Andric 
294824e7fdSDimitry Andric template <class _RealType = double>
30*cb14a3feSDimitry Andric class _LIBCPP_TEMPLATE_VIS exponential_distribution {
315f757f3fSDimitry Andric   static_assert(__libcpp_random_is_valid_realtype<_RealType>::value,
325f757f3fSDimitry Andric                 "RealType must be a supported floating-point type");
335f757f3fSDimitry Andric 
344824e7fdSDimitry Andric public:
354824e7fdSDimitry Andric   // types
364824e7fdSDimitry Andric   typedef _RealType result_type;
374824e7fdSDimitry Andric 
38*cb14a3feSDimitry Andric   class _LIBCPP_TEMPLATE_VIS param_type {
394824e7fdSDimitry Andric     result_type __lambda_;
40*cb14a3feSDimitry Andric 
414824e7fdSDimitry Andric   public:
424824e7fdSDimitry Andric     typedef exponential_distribution distribution_type;
434824e7fdSDimitry Andric 
__lambda_(__lambda)44*cb14a3feSDimitry Andric     _LIBCPP_HIDE_FROM_ABI explicit param_type(result_type __lambda = 1) : __lambda_(__lambda) {}
454824e7fdSDimitry Andric 
lambda()46*cb14a3feSDimitry Andric     _LIBCPP_HIDE_FROM_ABI result_type lambda() const { return __lambda_; }
474824e7fdSDimitry Andric 
48*cb14a3feSDimitry Andric     friend _LIBCPP_HIDE_FROM_ABI bool operator==(const param_type& __x, const param_type& __y) {
49*cb14a3feSDimitry Andric       return __x.__lambda_ == __y.__lambda_;
50*cb14a3feSDimitry Andric     }
51*cb14a3feSDimitry Andric     friend _LIBCPP_HIDE_FROM_ABI bool operator!=(const param_type& __x, const param_type& __y) { return !(__x == __y); }
524824e7fdSDimitry Andric   };
534824e7fdSDimitry Andric 
544824e7fdSDimitry Andric private:
554824e7fdSDimitry Andric   param_type __p_;
564824e7fdSDimitry Andric 
574824e7fdSDimitry Andric public:
584824e7fdSDimitry Andric   // constructors and reset functions
594824e7fdSDimitry Andric #ifndef _LIBCPP_CXX03_LANG
exponential_distribution()60*cb14a3feSDimitry Andric   _LIBCPP_HIDE_FROM_ABI exponential_distribution() : exponential_distribution(1) {}
exponential_distribution(result_type __lambda)61*cb14a3feSDimitry Andric   _LIBCPP_HIDE_FROM_ABI explicit exponential_distribution(result_type __lambda) : __p_(param_type(__lambda)) {}
624824e7fdSDimitry Andric #else
63*cb14a3feSDimitry Andric   _LIBCPP_HIDE_FROM_ABI explicit exponential_distribution(result_type __lambda = 1) : __p_(param_type(__lambda)) {}
644824e7fdSDimitry Andric #endif
exponential_distribution(const param_type & __p)65*cb14a3feSDimitry Andric   _LIBCPP_HIDE_FROM_ABI explicit exponential_distribution(const param_type& __p) : __p_(__p) {}
reset()66*cb14a3feSDimitry Andric   _LIBCPP_HIDE_FROM_ABI void reset() {}
674824e7fdSDimitry Andric 
684824e7fdSDimitry Andric   // generating functions
694824e7fdSDimitry Andric   template <class _URNG>
operator()70*cb14a3feSDimitry Andric   _LIBCPP_HIDE_FROM_ABI result_type operator()(_URNG& __g) {
71*cb14a3feSDimitry Andric     return (*this)(__g, __p_);
72*cb14a3feSDimitry Andric   }
7306c3fb27SDimitry Andric   template <class _URNG>
7406c3fb27SDimitry Andric   _LIBCPP_HIDE_FROM_ABI result_type operator()(_URNG& __g, const param_type& __p);
754824e7fdSDimitry Andric 
764824e7fdSDimitry Andric   // property functions
lambda()77*cb14a3feSDimitry Andric   _LIBCPP_HIDE_FROM_ABI result_type lambda() const { return __p_.lambda(); }
784824e7fdSDimitry Andric 
param()79*cb14a3feSDimitry Andric   _LIBCPP_HIDE_FROM_ABI param_type param() const { return __p_; }
param(const param_type & __p)80*cb14a3feSDimitry Andric   _LIBCPP_HIDE_FROM_ABI void param(const param_type& __p) { __p_ = __p; }
814824e7fdSDimitry Andric 
min()82*cb14a3feSDimitry Andric   _LIBCPP_HIDE_FROM_ABI result_type min() const { return 0; }
max()83*cb14a3feSDimitry Andric   _LIBCPP_HIDE_FROM_ABI result_type max() const { return numeric_limits<result_type>::infinity(); }
844824e7fdSDimitry Andric 
85*cb14a3feSDimitry Andric   friend _LIBCPP_HIDE_FROM_ABI bool
86*cb14a3feSDimitry Andric   operator==(const exponential_distribution& __x, const exponential_distribution& __y) {
87*cb14a3feSDimitry Andric     return __x.__p_ == __y.__p_;
88*cb14a3feSDimitry Andric   }
89*cb14a3feSDimitry Andric   friend _LIBCPP_HIDE_FROM_ABI bool
90*cb14a3feSDimitry Andric   operator!=(const exponential_distribution& __x, const exponential_distribution& __y) {
91*cb14a3feSDimitry Andric     return !(__x == __y);
92*cb14a3feSDimitry Andric   }
934824e7fdSDimitry Andric };
944824e7fdSDimitry Andric 
954824e7fdSDimitry Andric template <class _RealType>
964824e7fdSDimitry Andric template <class _URNG>
operator()97*cb14a3feSDimitry Andric _RealType exponential_distribution<_RealType>::operator()(_URNG& __g, const param_type& __p) {
9881ad6265SDimitry Andric   static_assert(__libcpp_random_is_valid_urng<_URNG>::value, "");
99*cb14a3feSDimitry Andric   return -std::log(result_type(1) - std::generate_canonical<result_type, numeric_limits<result_type>::digits>(__g)) /
100*cb14a3feSDimitry Andric          __p.lambda();
1014824e7fdSDimitry Andric }
1024824e7fdSDimitry Andric 
1034824e7fdSDimitry Andric template <class _CharT, class _Traits, class _RealType>
104bdd1243dSDimitry Andric _LIBCPP_HIDE_FROM_ABI basic_ostream<_CharT, _Traits>&
105*cb14a3feSDimitry Andric operator<<(basic_ostream<_CharT, _Traits>& __os, const exponential_distribution<_RealType>& __x) {
1064824e7fdSDimitry Andric   __save_flags<_CharT, _Traits> __lx(__os);
1074824e7fdSDimitry Andric   typedef basic_ostream<_CharT, _Traits> _OStream;
108*cb14a3feSDimitry Andric   __os.flags(_OStream::dec | _OStream::left | _OStream::fixed | _OStream::scientific);
1094824e7fdSDimitry Andric   return __os << __x.lambda();
1104824e7fdSDimitry Andric }
1114824e7fdSDimitry Andric 
1124824e7fdSDimitry Andric template <class _CharT, class _Traits, class _RealType>
113bdd1243dSDimitry Andric _LIBCPP_HIDE_FROM_ABI basic_istream<_CharT, _Traits>&
114*cb14a3feSDimitry Andric operator>>(basic_istream<_CharT, _Traits>& __is, exponential_distribution<_RealType>& __x) {
1154824e7fdSDimitry Andric   typedef exponential_distribution<_RealType> _Eng;
1164824e7fdSDimitry Andric   typedef typename _Eng::result_type result_type;
1174824e7fdSDimitry Andric   typedef typename _Eng::param_type param_type;
1184824e7fdSDimitry Andric   __save_flags<_CharT, _Traits> __lx(__is);
1194824e7fdSDimitry Andric   typedef basic_istream<_CharT, _Traits> _Istream;
1204824e7fdSDimitry Andric   __is.flags(_Istream::dec | _Istream::skipws);
1214824e7fdSDimitry Andric   result_type __lambda;
1224824e7fdSDimitry Andric   __is >> __lambda;
1234824e7fdSDimitry Andric   if (!__is.fail())
1244824e7fdSDimitry Andric     __x.param(param_type(__lambda));
1254824e7fdSDimitry Andric   return __is;
1264824e7fdSDimitry Andric }
1274824e7fdSDimitry Andric 
1284824e7fdSDimitry Andric _LIBCPP_END_NAMESPACE_STD
1294824e7fdSDimitry Andric 
1304824e7fdSDimitry Andric _LIBCPP_POP_MACROS
1314824e7fdSDimitry Andric 
1324824e7fdSDimitry Andric #endif // _LIBCPP___RANDOM_EXPONENTIAL_DISTRIBUTION_H
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