# 29 Numerics library [numerics]

## 29.6 Random number generation [rand]

### 29.6.8 Random number distribution class templates [rand.dist]

#### 29.6.8.3.4 Class template negative_­binomial_­distribution[rand.dist.bern.negbin]

A negative_­binomial_­distribution random number distribution produces random integers i0 distributed according to the discrete probability function

P(i|k,p)=(k+i1i)pk(1p)i.

[Note: This implies that P(i|k,p) is undefined when p == 1. end note]

```template<class IntType = int>
class negative_binomial_distribution {
public:
// types
using result_type = IntType;
using param_type  = unspecified;

// constructor and reset functions
explicit negative_binomial_distribution(IntType k = 1, double p = 0.5);
explicit negative_binomial_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
IntType k() const;
double p() const;
param_type param() const;
void param(const param_type& parm);
result_type min() const;
result_type max() const;
};```

```explicit negative_binomial_distribution(IntType k = 1, double p = 0.5); ```

Requires: 0<p1 and 0<k.

Effects: Constructs a negative_­binomial_­distribution object; k and p correspond to the respective parameters of the distribution.

```IntType k() const; ```

Returns: The value of the k parameter with which the object was constructed.

```double p() const; ```

Returns: The value of the p parameter with which the object was constructed.