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Showing content from https://cplusplus.com/reference/random/geometric_distribution/ below:

class template

std::geometric_distribution

template <class IntType = int> class geometric_distribution;

Geometric distribution

Random number distribution that produces integers according to a geometric discrete distribution, which is described by the following probability mass function:

This distribution produces positive random integers where each value represents the number of unsuccessful trials before a first success in a sequence of trials, each with a probability of success equal to p.

The distribution parameter, p, is set on construction.

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

Its analogous continuous distribution is the exponential_distribution.

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 geometric_distribution:

member type definition notes result_type The first template parameter (IntType) The type of the numbers generated (defaults to int) param_type not specified The type returned by member param.

Member functions

(constructor): Construct geometric distribution (public member function)

operator(): Generate random number (public member function)

reset: Reset distribution (public member function)

param: Distribution parameters (public member function)

min: Minimum value (public member function)

max: Maximum value (public member function)

Distribution parameters:

p: Probability of success (public member function)

Non-member functions

operator<<: Insert into output stream (function template)

operator>>: Extract from input stream (function template)

relational operators: Relational operators (function template)

Example

// geometric_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::geometric_distribution<int> distribution(0.3);

  int p[10]={};

  for (int i=0; i<nrolls; ++i) {
    int number = distribution(generator);
    if (number<10) ++p[number];
  }

  std::cout << "geometric_distribution (0.3):" << std::endl;
  for (int i=0; i<10; ++i)
    std::cout << i << ": " << std::string(p[i]*nstars/nrolls,'*') << std::endl;

  return 0;
}

Possible output:

geometric_distribution (0.3):
0: *****************************
1: *********************
2: **************
3: *********
4: *******
5: *****
6: ***
7: **
8: *
9: *