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]

26.6.9.4.1 Class template poisson_­distribution [rand.dist.pois.poisson]

A poisson_­distribution random number distribution produces integer values distributed according to the discrete probability function
The distribution parameter μ is also known as this distribution's mean.
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(); // 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; };
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.

26.6.9.4.2 Class template exponential_­distribution [rand.dist.pois.exp]

An exponential_­distribution random number distribution produces random numbers distributed according to the probability density function
template<class RealType = double> class exponential_distribution { public: // types using result_type = RealType; using param_type = unspecified; // constructors and reset functions exponential_distribution() : exponential_distribution(1.0) {} explicit exponential_distribution(RealType lambda); explicit exponential_distribution(const param_type& parm); void reset(); // 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 lambda() const; param_type param() const; void param(const param_type& parm); result_type min() const; result_type max() const; };
explicit exponential_distribution(RealType lambda);
Preconditions: .
Remarks: lambda corresponds to the parameter of the distribution.
RealType lambda() const;
Returns: The value of the lambda parameter with which the object was constructed.

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(); // 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; };
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.

26.6.9.4.4 Class template weibull_­distribution [rand.dist.pois.weibull]

A weibull_­distribution random number distribution produces random numbers distributed according to the probability density function
template<class RealType = double> class weibull_distribution { public: // types using result_type = RealType; using param_type = unspecified; // constructor and reset functions weibull_distribution() : weibull_distribution(1.0) {} explicit weibull_distribution(RealType a, RealType b = 1.0); explicit weibull_distribution(const param_type& parm); void reset(); // 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 a() const; RealType b() const; param_type param() const; void param(const param_type& parm); result_type min() const; result_type max() const; };
explicit weibull_distribution(RealType a, RealType b = 1.0);
Preconditions: and .
Remarks: a and b correspond to the respective parameters of the distribution.
RealType a() const;
Returns: The value of the a parameter with which the object was constructed.
RealType b() const;
Returns: The value of the b parameter with which the object was constructed.

26.6.9.4.5 Class template extreme_­value_­distribution [rand.dist.pois.extreme]

An extreme_­value_­distribution random number distribution produces random numbers x distributed according to the probability density function249
template<class RealType = double> class extreme_value_distribution { public: // types using result_type = RealType; using param_type = unspecified; // constructor and reset functions extreme_value_distribution() : extreme_value_distribution(0.0) {} explicit extreme_value_distribution(RealType a, RealType b = 1.0); explicit extreme_value_distribution(const param_type& parm); void reset(); // 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 a() const; RealType b() const; param_type param() const; void param(const param_type& parm); result_type min() const; result_type max() const; };
explicit extreme_value_distribution(RealType a, RealType b = 1.0);
Preconditions: .
Remarks: a and b correspond to the respective parameters of the distribution.
RealType a() const;
Returns: The value of the a parameter with which the object was constructed.
RealType b() const;
Returns: The value of the b parameter with which the object was constructed.
The distribution corresponding to this probability density function is also known (with a possible change of variable) as the Gumbel Type I, the log-Weibull, or the Fisher-Tippett Type I distribution.