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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_NEGATIVE_BINOMIAL_DISTRIBUTION_H
#define _LIBCPP___RANDOM_NEGATIVE_BINOMIAL_DISTRIBUTION_H
#include <__config>
#include <__random/bernoulli_distribution.h>
#include <__random/gamma_distribution.h>
#include <__random/is_valid.h>
#include <__random/poisson_distribution.h>
#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 _IntType = int>
class _LIBCPP_TEMPLATE_VIS negative_binomial_distribution
{
static_assert(__libcpp_random_is_valid_inttype<_IntType>::value, "IntType must be a supported integer type");
public:
// types
typedef _IntType result_type;
class _LIBCPP_TEMPLATE_VIS param_type
{
result_type __k_;
double __p_;
public:
typedef negative_binomial_distribution distribution_type;
_LIBCPP_INLINE_VISIBILITY
explicit param_type(result_type __k = 1, double __p = 0.5)
: __k_(__k), __p_(__p) {}
_LIBCPP_INLINE_VISIBILITY
result_type k() const {return __k_;}
_LIBCPP_INLINE_VISIBILITY
double p() const {return __p_;}
friend _LIBCPP_INLINE_VISIBILITY
bool operator==(const param_type& __x, const param_type& __y)
{return __x.__k_ == __y.__k_ && __x.__p_ == __y.__p_;}
friend _LIBCPP_INLINE_VISIBILITY
bool operator!=(const param_type& __x, const param_type& __y)
{return !(__x == __y);}
};
private:
param_type __p_;
public:
// constructor and reset functions
#ifndef _LIBCPP_CXX03_LANG
_LIBCPP_INLINE_VISIBILITY
negative_binomial_distribution() : negative_binomial_distribution(1) {}
_LIBCPP_INLINE_VISIBILITY
explicit negative_binomial_distribution(result_type __k, double __p = 0.5)
: __p_(__k, __p) {}
#else
_LIBCPP_INLINE_VISIBILITY
explicit negative_binomial_distribution(result_type __k = 1,
double __p = 0.5)
: __p_(__k, __p) {}
#endif
_LIBCPP_INLINE_VISIBILITY
explicit negative_binomial_distribution(const param_type& __p) : __p_(__p) {}
_LIBCPP_INLINE_VISIBILITY
void reset() {}
// generating functions
template<class _URNG>
_LIBCPP_INLINE_VISIBILITY
result_type operator()(_URNG& __g)
{return (*this)(__g, __p_);}
template<class _URNG> result_type operator()(_URNG& __g, const param_type& __p);
// property functions
_LIBCPP_INLINE_VISIBILITY
result_type k() const {return __p_.k();}
_LIBCPP_INLINE_VISIBILITY
double p() const {return __p_.p();}
_LIBCPP_INLINE_VISIBILITY
param_type param() const {return __p_;}
_LIBCPP_INLINE_VISIBILITY
void param(const param_type& __p) {__p_ = __p;}
_LIBCPP_INLINE_VISIBILITY
result_type min() const {return 0;}
_LIBCPP_INLINE_VISIBILITY
result_type max() const {return numeric_limits<result_type>::max();}
friend _LIBCPP_INLINE_VISIBILITY
bool operator==(const negative_binomial_distribution& __x,
const negative_binomial_distribution& __y)
{return __x.__p_ == __y.__p_;}
friend _LIBCPP_INLINE_VISIBILITY
bool operator!=(const negative_binomial_distribution& __x,
const negative_binomial_distribution& __y)
{return !(__x == __y);}
};
template <class _IntType>
template<class _URNG>
_IntType
negative_binomial_distribution<_IntType>::operator()(_URNG& __urng, const param_type& __pr)
{
static_assert(__libcpp_random_is_valid_urng<_URNG>::value, "");
result_type __k = __pr.k();
double __p = __pr.p();
// When the number of bits in _IntType is small, we are too likely to
// overflow __f below to use this technique.
if (__k <= 21 * __p && sizeof(_IntType) > 1)
{
bernoulli_distribution __gen(__p);
result_type __f = 0;
result_type __s = 0;
while (__s < __k)
{
if (__gen(__urng))
++__s;
else
++__f;
}
_LIBCPP_ASSERT(__f >= 0, "std::negative_binomial_distribution should never produce negative values. "
"This is almost certainly a signed integer overflow issue on __f.");
return __f;
}
return poisson_distribution<result_type>(gamma_distribution<double>
(__k, (1-__p)/__p)(__urng))(__urng);
}
template <class _CharT, class _Traits, class _IntType>
basic_ostream<_CharT, _Traits>&
operator<<(basic_ostream<_CharT, _Traits>& __os,
const negative_binomial_distribution<_IntType>& __x)
{
__save_flags<_CharT, _Traits> __lx(__os);
typedef basic_ostream<_CharT, _Traits> _OStream;
__os.flags(_OStream::dec | _OStream::left | _OStream::fixed |
_OStream::scientific);
_CharT __sp = __os.widen(' ');
__os.fill(__sp);
return __os << __x.k() << __sp << __x.p();
}
template <class _CharT, class _Traits, class _IntType>
basic_istream<_CharT, _Traits>&
operator>>(basic_istream<_CharT, _Traits>& __is,
negative_binomial_distribution<_IntType>& __x)
{
typedef negative_binomial_distribution<_IntType> _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 __k;
double __p;
__is >> __k >> __p;
if (!__is.fail())
__x.param(param_type(__k, __p));
return __is;
}
_LIBCPP_END_NAMESPACE_STD
_LIBCPP_POP_MACROS
#endif // _LIBCPP___RANDOM_NEGATIVE_BINOMIAL_DISTRIBUTION_H
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