# 25 Numerics library [numerics]

## 25.6 Random number generation [rand]

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

#### 25.6.8.3.1 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
using result_type = bool;
using param_type  = unspecified;

// constructors and reset functions
bernoulli_distribution() : bernoulli_distribution(0.5) {}
explicit bernoulli_distribution(double p);
explicit bernoulli_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 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); 
Requires: .
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.

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

A binomial_­distribution random number distribution produces integer values distributed according to the discrete probability function
template<class IntType = int>
class binomial_distribution {
public:
// types
using result_type = IntType;
using param_type  = unspecified;

// constructors and reset functions
binomial_distribution() : binomial_distribution(1) {}
explicit binomial_distribution(IntType t, double p = 0.5);
explicit 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 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, double p = 0.5); 
Requires: and .
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.

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

A geometric_­distribution random number distribution produces integer values distributed according to the discrete probability function
template<class IntType = int>
class geometric_distribution {
public:
// types
using result_type = IntType;
using param_type  = unspecified;

// constructors and reset functions
geometric_distribution() : geometric_distribution(0.5) {}
explicit geometric_distribution(double p);
explicit geometric_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 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); 
Requires: .
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.

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

A negative_­binomial_­distribution random number distribution produces random integers distributed according to the discrete probability function
[Note
:
This implies that 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
negative_binomial_distribution() : negative_binomial_distribution(1) {}
explicit negative_binomial_distribution(IntType k, 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, double p = 0.5); 
Requires: and .
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.