# 29 Numerics library [numerics]

## 29.6 Random number generation [rand]

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

#### 29.6.8.2.1 Class template uniform_­int_­distribution[rand.dist.uni.int]

A uniform_­int_­distribution random number distribution produces random integers i, aib, distributed according to the constant discrete probability function

P(i|a,b)=1/(ba+1).

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

// constructors and reset functions
explicit uniform_int_distribution(IntType a = 0, IntType b = numeric_limits<IntType>::max());
explicit uniform_int_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
result_type a() const;
result_type b() const;
param_type param() const;
void param(const param_type& parm);
result_type min() const;
result_type max() const;
};

explicit uniform_int_distribution(IntType a = 0, IntType b = numeric_limits<IntType>::max());

Requires: ab.

Effects: Constructs a uniform_­int_­distribution object; a and b correspond to the respective parameters of the distribution.

result_type a() const;

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

result_type b() const;

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

#### 29.6.8.2.2 Class template uniform_­real_­distribution[rand.dist.uni.real]

A uniform_­real_­distribution random number distribution produces random numbers x, ax<b, distributed according to the constant probability density function

p(x|a,b)=1/(ba).

[Note: This implies that p(x|a,b) is undefined when a == b. end note]

template<class RealType = double>
class uniform_real_distribution {
public:
// types
using result_type = RealType;
using param_type  = unspecified;

// constructors and reset functions
explicit uniform_real_distribution(RealType a = 0.0, RealType b = 1.0);
explicit uniform_real_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
result_type a() const;
result_type b() const;
param_type param() const;
void param(const param_type& parm);
result_type min() const;
result_type max() const;
};

explicit uniform_real_distribution(RealType a = 0.0, RealType b = 1.0);

Requires: ab and banumeric_limits<RealType>::max().

Effects: Constructs a uniform_­real_­distribution object; a and b correspond to the respective parameters of the distribution.

result_type a() const;

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

result_type b() const;

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