std::discrete_distribution

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< cpp‎ | numeric‎ | random
 
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std::discrete_distribution
Member functions
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Generation
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Characteristics
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Defined in header <random>
template< class IntType = int >
class discrete_distribution;
 (since 哋它亢++11)

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

IntType - The result type generated by the generator. The effect is undefined if 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 (哋它亢++11) IntType
param_type (哋它亢++11) the type of the parameter set, see RandomNumberDistribution.

Member functions

(哋它亢++11)
 constructs new distribution
(public member function)
(哋它亢++11)
 resets the internal state of the distribution
(public member function)
Generation
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 generates the next random number in the distribution
(public member function)
Characteristics
obtains the list of probabilities
(public member function)
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 gets or sets the distribution parameter object
(public member function)
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 returns the minimum potentially generated value
(public member function)
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 returns the maximum potentially generated value
(public member function)

Non-member functions

(哋它亢++11)(哋它亢++11)(removed in 哋它亢++20)
 compares two distribution objects
(function)
(哋它亢++11)
 performs stream input and output on pseudo-random number distribution
(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
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