Provided by: libstdc++6-4.4-doc_4.4.7-1ubuntu2_all

#### NAME

```       std::poisson_distribution< _IntType, _RealType > -

```

#### SYNOPSIS

```   Public Types
typedef _RealType input_type
typedef _IntType result_type

Public Member Functions
_RealType mean () const
template<class _UniformRandomNumberGenerator > result_type operator()
(_UniformRandomNumberGenerator &__urng)
poisson_distribution (const _RealType &__mean=_RealType(1))
void reset ()

Friends
template<typename _IntType1 , typename _RealType1 , typename _CharT , typename _Traits >
std::basic_ostream< _CharT,
_Traits > & operator<< (std::basic_ostream< _CharT, _Traits > &__os, const
poisson_distribution< _IntType1, _RealType1 > &__x)"
template<typename _IntType1 , typename _RealType1 , typename _CharT , typename _Traits >
std::basic_istream< _CharT,
_Traits > & operator>> (std::basic_istream< _CharT, _Traits > &__is,
poisson_distribution< _IntType1, _RealType1 > &__x)"

```

#### DetailedDescription

```   template<typename _IntType = int, typename _RealType = double>class std::poisson_distribution<
_IntType, _RealType >
A discrete Poisson random number distribution.

The formula for the Poisson probability mass function is \$ p(i) = ac{mean^i}{i!} e^{-mean}
\$ where \$ mean \$ is the parameter of the distribution.

Definition at line 1864 of file tr1_impl/random.

```

#### MemberFunctionDocumentation

```   template<typename _IntType = int, typename _RealType = double> _RealType
std::poisson_distribution< _IntType, _RealType >::mean () const [inline] Gets the
distribution parameter mean.
Definition at line 1884 of file tr1_impl/random.

template<typename _IntType , typename _RealType > template<class _UniformRandomNumberGenerator
> poisson_distribution< _IntType, _RealType >::result_type std::poisson_distribution<
_IntType, _RealType >::operator() (_UniformRandomNumberGenerator &__urng) A rejection
algorithm when mean >= 12 and a simple method based upon the multiplication of uniform
random variates otherwise. NB: The former is available only if _GLIBCXX_USE_C99_MATH_TR1
is defined.
Reference: Devroye, L. 'Non-Uniform Random Variates Generation.' Springer-Verlag, New
York, 1986, Ch. X, Sects. 3.3 & 3.4 (+ Errata!).

Definition at line 936 of file random.tcc.

References std::abs(), std::log(), and std::max().

```

#### FriendsAndRelatedFunctionDocumentation

```   template<typename _IntType = int, typename _RealType = double> template<typename _IntType1 ,
typename _RealType1 , typename _CharT , typename _Traits > std::basic_ostream<_CharT,
_Traits>& operator<< (std::basic_ostream< _CharT, _Traits > &__os, const
poisson_distribution< _IntType1, _RealType1 > &__x) [friend] Inserts a
poisson_distribution random number distribution __x into the output stream __os.
Parameters:
__os An output stream.
__x A poisson_distribution random number distribution.

Returns:
The output stream with the state of __x inserted or in an error state.

template<typename _IntType = int, typename _RealType = double> template<typename _IntType1 ,
typename _RealType1 , typename _CharT , typename _Traits > std::basic_istream<_CharT,
_Traits>& operator>> (std::basic_istream< _CharT, _Traits > &__is, poisson_distribution<
_IntType1, _RealType1 > &__x) [friend] Extracts a poisson_distribution random number
distribution __x from the input stream __is.
Parameters:
__is An input stream.
__x A poisson_distribution random number generator engine.

Returns:
The input stream with __x extracted or in an error state.

```

#### Author

```       Generated automatically by Doxygen for libstdc++ from the source code.

libstdc++                                Mostd::poisson2distribution< _IntType, _RealType >(3cxx)
```