26 Numerics library [numerics]

26.6 Random number generation [rand]

26.6.9 Random number distribution class templates [rand.dist]

26.6.9.4 Poisson distributions [rand.dist.pois]

26.6.9.4.3 Class template gamma_­distribution [rand.dist.pois.gamma]

A gamma_­distribution random number distribution produces random numbers distributed according to the probability density function
template<class RealType = double> class gamma_distribution { public: // types using result_type = RealType; using param_type = unspecified; // constructors and reset functions gamma_distribution() : gamma_distribution(1.0) {} explicit gamma_distribution(RealType alpha, RealType beta = 1.0); explicit gamma_distribution(const param_type& parm); void reset(); // equality operators friend bool operator==(const gamma_distribution& x, const gamma_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 RealType alpha() const; RealType beta() 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 gamma_distribution& x); template<class charT, class traits> friend basic_istream<charT, traits>& operator>>(basic_istream<charT, traits>& is, gamma_distribution& x); };
explicit gamma_distribution(RealType alpha, RealType beta = 1.0);
Preconditions: and .
Remarks: alpha and beta correspond to the parameters of the distribution.
RealType alpha() const;
Returns: The value of the alpha parameter with which the object was constructed.
RealType beta() const;
Returns: The value of the beta parameter with which the object was constructed.