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