# 26 Numerics library [numerics]

## 26.5 Random number generation [rand]

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

#### 26.5.8.3.1 Class bernoulli_distribution[rand.dist.bern.bernoulli]

A bernoulli_distribution random number distribution produces bool values b distributed according to the discrete probability function

class bernoulli_distribution{
public:
// types
typedef bool result_type;
typedef unspecified param_type;

// constructors and reset functions
explicit bernoulli_distribution(double p = 0.5);
explicit bernoulli_distribution(const param_type& parm);
void reset();

// generating functions
template<class URNG>
result_type operator()(URNG& g);
template<class URNG>
result_type operator()(URNG& g, const param_type& parm);

// property functions
double p() const;
param_type param() const;
void param(const param_type& parm);
result_type min() const;
result_type max() const;
};


 explicit bernoulli_distribution(double p = 0.5); 

Requires: 0 ≤ p ≤ 1.

Effects: Constructs a bernoulli_distribution object; p corresponds to the parameter of the distribution.

 double p() const; 

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

#### 26.5.8.3.2 Class template binomial_distribution[rand.dist.bern.bin]

A binomial_distribution random number distribution produces integer values i ≥ 0 distributed according to the discrete probability function

template<class IntType = int>
class binomial_distribution{
public:
// types
typedef IntType result_type;
typedef unspecified param_type;

// constructors and reset functions
explicit binomial_distribution(IntType t = 1, double p = 0.5);
explicit binomial_distribution(const param_type& parm);
void reset();

// generating functions
template<class URNG>
result_type operator()(URNG& g);
template<class URNG>
result_type operator()(URNG& g, const param_type& parm);

// property functions
IntType t() const;
double p() const;
param_type param() const;
void param(const param_type& parm);
result_type min() const;
result_type max() const;
};


 explicit binomial_distribution(IntType t = 1, double p = 0.5); 

Requires: 0 ≤ p ≤ 1 and 0 ≤ t .

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

 IntType t() const; 

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

 double p() const; 

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

#### 26.5.8.3.3 Class template geometric_distribution[rand.dist.bern.geo]

A geometric_distribution random number distribution produces integer values i ≥ 0 distributed according to the discrete probability function P(i | p) = p · (1-p)i .

template<class IntType = int>
class geometric_distribution{
public:
// types
typedef IntType result_type;
typedef unspecified param_type;

// constructors and reset functions
explicit geometric_distribution(double p = 0.5);
explicit geometric_distribution(const param_type& parm);
void reset();

// generating functions
template<class URNG>
result_type operator()(URNG& g);
template<class URNG>
result_type operator()(URNG& g, const param_type& parm);

// property functions
double p() const;
param_type param() const;
void param(const param_type& parm);
result_type min() const;
result_type max() const;
};


 explicit geometric_distribution(double p = 0.5); 

Requires: 0 < p < 1.

Effects: Constructs a geometric_distribution object; p corresponds to the parameter of the distribution.

 double p() const; 

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

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

A negative_binomial_distribution random number distribution produces random integers i ≥ 0 distributed according to the discrete probability function

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

// 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 URNG>
result_type operator()(URNG& g);
template<class URNG>
result_type operator()(URNG& 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 < p ≤ 1 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.