Class template poisson_distribution

boost::random::poisson_distribution

Synopsis

// In header: <boost/random/poisson_distribution.hpp>

template<typename IntType = int, typename RealType = double> 
class poisson_distribution {
public:
  // types
  typedef IntType  result_type;
  typedef RealType input_type; 

  // member classes/structs/unions

  class param_type {
  public:
    // types
    typedef poisson_distribution distribution_type;

    // public member functions
    explicit param_type(RealType = 1);
    RealType mean() const;

    // friend functions
    template<typename CharT, typename Traits> 
      std::basic_ostream< CharT, Traits > & 
      operator<<(std::basic_ostream< CharT, Traits > &, const param_type &);
    template<typename CharT, typename Traits> 
      std::basic_istream< CharT, Traits > & 
      operator>>(std::basic_istream< CharT, Traits > &, param_type &);
    bool operator==(const param_type &, const param_type &);
    bool operator!=(const param_type &, const param_type &);
  };

  // public member functions
  explicit poisson_distribution(RealType = 1);
  explicit poisson_distribution(const param_type &);
  template<typename URNG> IntType operator()(URNG &) const;
  template<typename URNG> IntType operator()(URNG &, const param_type &) const;
  RealType mean() const;
  IntType min() const;
  IntType max() const;
  param_type param() const;
  void param(const param_type &);
  void reset();

  // friend functions
  template<typename CharT, typename Traits> 
    std::basic_ostream< CharT, Traits > & 
    operator<<(std::basic_ostream< CharT, Traits > &, 
               const poisson_distribution &);
  template<typename CharT, typename Traits> 
    std::basic_istream< CharT, Traits > & 
    operator>>(std::basic_istream< CharT, Traits > &, poisson_distribution &);
  bool operator==(const poisson_distribution &, const poisson_distribution &);
  bool operator!=(const poisson_distribution &, const poisson_distribution &);
};

Description

An instantiation of the class template poisson_distribution is a model of random distribution . The poisson distribution has

This implementation is based on the PTRD algorithm described

"The transformed rejection method for generating Poisson random variables", Wolfgang Hormann, Insurance: Mathematics and Economics Volume 12, Issue 1, February 1993, Pages 39-45

`poisson_distribution` public member functions

```
explicit poisson_distribution(RealType mean = 1);
```
Constructs a poisson_distribution with the parameter mean.

Requires: mean > 0

explicit poisson_distribution(const param_type & param);

Construct an poisson_distribution object from the parameters.

```
template<typename URNG> IntType operator()(URNG & urng) const;
```
Returns a random variate distributed according to the poisson distribution.
```
template<typename URNG> 
  IntType operator()(URNG & urng, const param_type & param) const;
```
Returns a random variate distributed according to the poisson distribution with parameters specified by param.
```
RealType mean() const;
```
Returns the "mean" parameter of the distribution.
```
IntType min() const;
```
Returns the smallest value that the distribution can produce.
```
IntType max() const;
```
Returns the largest value that the distribution can produce.
```
param_type param() const;
```
Returns the parameters of the distribution.
```
void param(const param_type & param);
```
Sets parameters of the distribution.
```
void reset();
```
Effects: Subsequent uses of the distribution do not depend on values produced by any engine prior to invoking reset.

`poisson_distribution` friend functions

template<typename CharT, typename Traits> 
  std::basic_ostream< CharT, Traits > & 
  operator<<(std::basic_ostream< CharT, Traits > & os, 
             const poisson_distribution & pd);

Writes the parameters of the distribution to a std::ostream.

template<typename CharT, typename Traits> 
  std::basic_istream< CharT, Traits > & 
  operator>>(std::basic_istream< CharT, Traits > & is, 
             poisson_distribution & pd);

Reads the parameters of the distribution from a std::istream.

bool operator==(const poisson_distribution & lhs, 
                const poisson_distribution & rhs);

Returns true if the two distributions will produce the same sequence of values, given equal generators.

bool operator!=(const poisson_distribution & lhs, 
                const poisson_distribution & rhs);

Returns true if the two distributions could produce different sequences of values, given equal generators.

Boost C++ Libraries

Class template poisson_distribution

Synopsis

Description

poisson_distribution public member functions

poisson_distribution friend functions

`poisson_distribution` public member functions

`poisson_distribution` friend functions