NAME¶

std::discrete_distribution - std::discrete_distribution

Synopsis¶

Defined in header <random>
template< class IntType = int > (since C++11)
class discrete_distribution;

std::discrete_distribution produces random integers on the interval [0, n), where
the probability of each individual integer i is defined as w
i/S, that is the weight of the ith integer divided by the sum of all n weights.

std::discrete_distribution satisfies all requirements of RandomNumberDistribution.

Template parameters¶

The result type generated by the generator. The effect is undefined if
IntType - this is not one of short, int, long, long long, unsigned short, unsigned
int, unsigned long, or unsigned long long.

Member types¶

Member type Definition
result_type (C++11) IntType
param_type (C++11) the type of the parameter set, see RandomNumberDistribution.

Member functions¶

constructor constructs new distribution
(C++11) (public member function)
reset resets the internal state of the distribution
(C++11) (public member function)

Generation¶

operator() generates the next random number in the distribution
(C++11) (public member function)

Characteristics¶

probabilities obtains the list of probabilities
(public member function)
param gets or sets the distribution parameter object
(C++11) (public member function)
min returns the minimum potentially generated value
(C++11) (public member function)
max returns the maximum potentially generated value
(C++11) (public member function)

Non-member functions¶

operator==
operator!= compares two distribution objects
(C++11) (function)
(C++11)(removed in C++20)
operator<< performs stream input and output on pseudo-random number
operator>> distribution
(C++11) (function template)

Example¶

// Run this code

#include <iomanip>
#include <iostream>
#include <map>
#include <random>

int main()
{
std::random_device rd;
std::mt19937 gen(rd());
std::discrete_distribution<> d({40, 10, 10, 40});
std::map<int, int> map;

for (int n = 0; n < 1e4; ++n)
++map[d(gen)];

for (const auto& [num, count] : map)
std::cout << num << " generated " << std::setw(4) << count << " times\n";
}

Possible output:¶

0 generated 4037 times
1 generated 962 times
2 generated 1030 times
3 generated 3971 times