133 lines · c
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-exception6//7//===----------------------------------------------------------------------===//8 9#ifndef _LIBCPP___RANDOM_EXPONENTIAL_DISTRIBUTION_H10#define _LIBCPP___RANDOM_EXPONENTIAL_DISTRIBUTION_H11 12#include <__config>13#include <__random/generate_canonical.h>14#include <__random/is_valid.h>15#include <__random/uniform_real_distribution.h>16#include <cmath>17#include <iosfwd>18#include <limits>19 20#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)21# pragma GCC system_header22#endif23 24_LIBCPP_PUSH_MACROS25#include <__undef_macros>26 27_LIBCPP_BEGIN_NAMESPACE_STD28 29template <class _RealType = double>30class exponential_distribution {31 static_assert(__libcpp_random_is_valid_realtype<_RealType>::value,32 "RealType must be a supported floating-point type");33 34public:35 // types36 typedef _RealType result_type;37 38 class param_type {39 result_type __lambda_;40 41 public:42 typedef exponential_distribution distribution_type;43 44 _LIBCPP_HIDE_FROM_ABI explicit param_type(result_type __lambda = 1) : __lambda_(__lambda) {}45 46 _LIBCPP_HIDE_FROM_ABI result_type lambda() const { return __lambda_; }47 48 friend _LIBCPP_HIDE_FROM_ABI bool operator==(const param_type& __x, const param_type& __y) {49 return __x.__lambda_ == __y.__lambda_;50 }51 friend _LIBCPP_HIDE_FROM_ABI bool operator!=(const param_type& __x, const param_type& __y) { return !(__x == __y); }52 };53 54private:55 param_type __p_;56 57public:58 // constructors and reset functions59#ifndef _LIBCPP_CXX03_LANG60 _LIBCPP_HIDE_FROM_ABI exponential_distribution() : exponential_distribution(1) {}61 _LIBCPP_HIDE_FROM_ABI explicit exponential_distribution(result_type __lambda) : __p_(param_type(__lambda)) {}62#else63 _LIBCPP_HIDE_FROM_ABI explicit exponential_distribution(result_type __lambda = 1) : __p_(param_type(__lambda)) {}64#endif65 _LIBCPP_HIDE_FROM_ABI explicit exponential_distribution(const param_type& __p) : __p_(__p) {}66 _LIBCPP_HIDE_FROM_ABI void reset() {}67 68 // generating functions69 template <class _URNG>70 _LIBCPP_HIDE_FROM_ABI result_type operator()(_URNG& __g) {71 return (*this)(__g, __p_);72 }73 template <class _URNG>74 _LIBCPP_HIDE_FROM_ABI result_type operator()(_URNG& __g, const param_type& __p);75 76 // property functions77 _LIBCPP_HIDE_FROM_ABI result_type lambda() const { return __p_.lambda(); }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 bool86 operator==(const exponential_distribution& __x, const exponential_distribution& __y) {87 return __x.__p_ == __y.__p_;88 }89 friend _LIBCPP_HIDE_FROM_ABI bool90 operator!=(const exponential_distribution& __x, const exponential_distribution& __y) {91 return !(__x == __y);92 }93};94 95template <class _RealType>96template <class _URNG>97_RealType exponential_distribution<_RealType>::operator()(_URNG& __g, const param_type& __p) {98 static_assert(__libcpp_random_is_valid_urng<_URNG>::value, "");99 return -std::log(result_type(1) - std::generate_canonical<result_type, numeric_limits<result_type>::digits>(__g)) /100 __p.lambda();101}102 103template <class _CharT, class _Traits, class _RealType>104_LIBCPP_HIDE_FROM_ABI basic_ostream<_CharT, _Traits>&105operator<<(basic_ostream<_CharT, _Traits>& __os, const exponential_distribution<_RealType>& __x) {106 __save_flags<_CharT, _Traits> __lx(__os);107 typedef basic_ostream<_CharT, _Traits> _OStream;108 __os.flags(_OStream::dec | _OStream::left | _OStream::fixed | _OStream::scientific);109 return __os << __x.lambda();110}111 112template <class _CharT, class _Traits, class _RealType>113_LIBCPP_HIDE_FROM_ABI basic_istream<_CharT, _Traits>&114operator>>(basic_istream<_CharT, _Traits>& __is, exponential_distribution<_RealType>& __x) {115 typedef exponential_distribution<_RealType> _Eng;116 typedef typename _Eng::result_type result_type;117 typedef typename _Eng::param_type param_type;118 __save_flags<_CharT, _Traits> __lx(__is);119 typedef basic_istream<_CharT, _Traits> _Istream;120 __is.flags(_Istream::dec | _Istream::skipws);121 result_type __lambda;122 __is >> __lambda;123 if (!__is.fail())124 __x.param(param_type(__lambda));125 return __is;126}127 128_LIBCPP_END_NAMESPACE_STD129 130_LIBCPP_POP_MACROS131 132#endif // _LIBCPP___RANDOM_EXPONENTIAL_DISTRIBUTION_H133