28 Numerics library [numerics]

28.5 Random number generation [rand]

28.5.9 Random number distribution class templates [rand.dist] Poisson distributions [rand.dist.pois] Class template poisson_distribution [rand.dist.pois.poisson]

A poisson_distribution random number distribution produces integer values i  ≥ 0 distributed according to the discrete probability function
The distribution parameter μ is also known as this distribution's mean.
namespace std { template<class IntType = int> class poisson_distribution { public: // types using result_type = IntType; using param_type = unspecified; // constructors and reset functions poisson_distribution() : poisson_distribution(1.0) {} explicit poisson_distribution(double mean); explicit poisson_distribution(const param_type& parm); void reset(); // equality operators friend bool operator==(const poisson_distribution& x, const poisson_distribution& y); // generating functions template<class URBG> result_type operator()(URBG& g); template<class URBG> result_type operator()(URBG& g, const param_type& parm); // property functions double mean() const; param_type param() const; void param(const param_type& parm); result_type min() const; result_type max() const; // inserters and extractors template<class charT, class traits> friend basic_ostream<charT, traits>& operator<<(basic_ostream<charT, traits>& os, const poisson_distribution& x); template<class charT, class traits> friend basic_istream<charT, traits>& operator>>(basic_istream<charT, traits>& is, poisson_distribution& x); }; }
explicit poisson_distribution(double mean);
Preconditions: .
Remarks: mean corresponds to the parameter of the distribution.
double mean() const;
Returns: The value of the mean parameter with which the object was constructed.