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132 lines
4.6 KiB
C++
132 lines
4.6 KiB
C++
//===----------------------------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#ifndef _LIBCPP___RANDOM_EXPONENTIAL_DISTRIBUTION_H
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#define _LIBCPP___RANDOM_EXPONENTIAL_DISTRIBUTION_H
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#include <__config>
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#include <__random/generate_canonical.h>
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#include <__random/is_valid.h>
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#include <__random/uniform_real_distribution.h>
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#include <cmath>
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#include <iosfwd>
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#include <limits>
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#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
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# pragma GCC system_header
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#endif
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_LIBCPP_PUSH_MACROS
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#include <__undef_macros>
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_LIBCPP_BEGIN_NAMESPACE_STD
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template <class _RealType = double>
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class _LIBCPP_TEMPLATE_VIS exponential_distribution {
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static_assert(__libcpp_random_is_valid_realtype<_RealType>::value,
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"RealType must be a supported floating-point type");
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public:
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// types
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typedef _RealType result_type;
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class _LIBCPP_TEMPLATE_VIS param_type {
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result_type __lambda_;
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public:
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typedef exponential_distribution distribution_type;
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_LIBCPP_HIDE_FROM_ABI explicit param_type(result_type __lambda = 1) : __lambda_(__lambda) {}
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_LIBCPP_HIDE_FROM_ABI result_type lambda() const { return __lambda_; }
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friend _LIBCPP_HIDE_FROM_ABI bool operator==(const param_type& __x, const param_type& __y) {
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return __x.__lambda_ == __y.__lambda_;
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}
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friend _LIBCPP_HIDE_FROM_ABI bool operator!=(const param_type& __x, const param_type& __y) { return !(__x == __y); }
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};
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private:
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param_type __p_;
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public:
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// constructors and reset functions
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#ifndef _LIBCPP_CXX03_LANG
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_LIBCPP_HIDE_FROM_ABI exponential_distribution() : exponential_distribution(1) {}
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_LIBCPP_HIDE_FROM_ABI explicit exponential_distribution(result_type __lambda) : __p_(param_type(__lambda)) {}
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#else
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_LIBCPP_HIDE_FROM_ABI explicit exponential_distribution(result_type __lambda = 1) : __p_(param_type(__lambda)) {}
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#endif
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_LIBCPP_HIDE_FROM_ABI explicit exponential_distribution(const param_type& __p) : __p_(__p) {}
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_LIBCPP_HIDE_FROM_ABI void reset() {}
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// generating functions
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template <class _URNG>
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_LIBCPP_HIDE_FROM_ABI result_type operator()(_URNG& __g) {
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return (*this)(__g, __p_);
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}
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template <class _URNG>
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_LIBCPP_HIDE_FROM_ABI result_type operator()(_URNG& __g, const param_type& __p);
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// property functions
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_LIBCPP_HIDE_FROM_ABI result_type lambda() const { return __p_.lambda(); }
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_LIBCPP_HIDE_FROM_ABI param_type param() const { return __p_; }
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_LIBCPP_HIDE_FROM_ABI void param(const param_type& __p) { __p_ = __p; }
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_LIBCPP_HIDE_FROM_ABI result_type min() const { return 0; }
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_LIBCPP_HIDE_FROM_ABI result_type max() const { return numeric_limits<result_type>::infinity(); }
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friend _LIBCPP_HIDE_FROM_ABI bool
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operator==(const exponential_distribution& __x, const exponential_distribution& __y) {
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return __x.__p_ == __y.__p_;
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}
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friend _LIBCPP_HIDE_FROM_ABI bool
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operator!=(const exponential_distribution& __x, const exponential_distribution& __y) {
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return !(__x == __y);
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}
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};
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template <class _RealType>
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template <class _URNG>
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_RealType exponential_distribution<_RealType>::operator()(_URNG& __g, const param_type& __p) {
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static_assert(__libcpp_random_is_valid_urng<_URNG>::value, "");
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return -std::log(result_type(1) - std::generate_canonical<result_type, numeric_limits<result_type>::digits>(__g)) /
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__p.lambda();
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}
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template <class _CharT, class _Traits, class _RealType>
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_LIBCPP_HIDE_FROM_ABI basic_ostream<_CharT, _Traits>&
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operator<<(basic_ostream<_CharT, _Traits>& __os, const exponential_distribution<_RealType>& __x) {
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__save_flags<_CharT, _Traits> __lx(__os);
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typedef basic_ostream<_CharT, _Traits> _OStream;
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__os.flags(_OStream::dec | _OStream::left | _OStream::fixed | _OStream::scientific);
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return __os << __x.lambda();
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}
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template <class _CharT, class _Traits, class _RealType>
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_LIBCPP_HIDE_FROM_ABI basic_istream<_CharT, _Traits>&
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operator>>(basic_istream<_CharT, _Traits>& __is, exponential_distribution<_RealType>& __x) {
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typedef exponential_distribution<_RealType> _Eng;
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typedef typename _Eng::result_type result_type;
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typedef typename _Eng::param_type param_type;
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__save_flags<_CharT, _Traits> __lx(__is);
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typedef basic_istream<_CharT, _Traits> _Istream;
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__is.flags(_Istream::dec | _Istream::skipws);
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result_type __lambda;
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__is >> __lambda;
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if (!__is.fail())
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__x.param(param_type(__lambda));
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return __is;
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}
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_LIBCPP_END_NAMESPACE_STD
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_LIBCPP_POP_MACROS
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#endif // _LIBCPP___RANDOM_EXPONENTIAL_DISTRIBUTION_H
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