class template
<random>

std::binomial_distribution

template <class IntType = int> class binomial_distribution;
Binomial distribution
Random number distribution that produces integers according to a binomial discrete distribution, which is described by the following probability mass function:



This distribution produces random integers in the range [0,t], where each value represents the number of successes in a sequence of t trials (each with a probability of success equal to p).

The distribution parameters, t and p, are set on construction.

To produce a random value following this distribution, call its member function operator().

Template parameters

IntType
An integer type. Aliased as member type result_type.
By default, this is int.

Member types

The following aliases are member types of binomial_distribution:

member typedefinitionnotes
result_typeThe first template parameter (IntType)The type of the numbers generated (defaults to int)
param_typenot specifiedThe type returned by member param.

Member functions


Distribution parameters


Non-member functions


Example

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// binomial_distribution
#include <iostream>
#include <random>

int main()
{
  const int nrolls = 10000; // number of experiments
  const int nstars = 100;   // maximum number of stars to distribute

  std::default_random_engine generator;
  std::binomial_distribution<int> distribution(9,0.5);

  int p[10]={};

  for (int i=0; i<nrolls; ++i) {
    int number = distribution(generator);
    ++p[number];
  }

  std::cout << "binomial_distribution (9,0.5):" << std::endl;
  for (int i=0; i<10; ++i)
    std::cout << i << ": " << std::string(p[i]*nstars/nrolls,'*') << std::endl;

  return 0;
}

Possible output:
binomial_distribution (9,0.5):
0: 
1: *
2: ******
3: ****************
4: *************************
5: ************************
6: *****************
7: *****
8: *
9: 


See also