[rand.dist.pois.weibull]

# 29 Numerics library [[numerics]](./#numerics)

## 29.5 Random number generation [[rand]](rand#dist.pois.weibull)

### 29.5.9 Random number distribution class templates [[rand.dist]](rand.dist#pois.weibull)

#### 29.5.9.4 Poisson distributions [[rand.dist.pois]](rand.dist.pois#weibull)

#### 29.5.9.4.4 Class template weibull_distribution [rand.dist.pois.weibull]

[1](#1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L5435)

A weibull_distribution random number distribution
produces random numbers x â¥ 0 distributed according to
the probability density function in Formula [29.11](#eq:rand.dist.pois.weibull)[.](#1.sentence-1)

p(x|a,b)=abâ(xb)aâ1âexp(â(xb)a)(29.11)

[ð](#lib:weibull_distribution_)

namespace std {template<class RealType = double>class weibull_distribution {public:// typesusing 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(); // equality operatorsfriend bool operator==(const weibull_distribution& x, const weibull_distribution& y); // generating functionstemplate<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; // inserters and extractorstemplate<class charT, class traits>friend basic_ostream<charT, traits>&operator<<(basic_ostream<charT, traits>& os, const weibull_distribution& x); template<class charT, class traits>friend basic_istream<charT, traits>&operator>>(basic_istream<charT, traits>& is, weibull_distribution& x); };}

[ð](#lib:weibull_distribution,constructor)

`explicit weibull_distribution(RealType a, RealType b = 1.0);
`

[2](#2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L5497)

*Preconditions*: 0<a and 0<b[.](#2.sentence-1)

[3](#3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L5501)

*Remarks*: a and b correspond to the respective parameters of the distribution[.](#3.sentence-1)

[ð](#lib:a,weibull_distribution)

`RealType a() const;
`

[4](#4)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L5513)

*Returns*: The value of the a parameter
 with which the object was constructed[.](#4.sentence-1)

[ð](#lib:b,weibull_distribution)

`RealType b() const;
`

[5](#5)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L5525)

*Returns*: The value of the b parameter
 with which the object was constructed[.](#5.sentence-1)
