std::negative_binomial_distribution(3)

NAME
std::negative_binomial_distribution - std::negative_binomial_distribution

Synopsis
   Defined in header <random>
   template< class IntType = int > (since C++11)
   class negative_binomial_distribution;
   Produces random non-negative integer values i, distributed according to discrete
   probability function:
   \(P(i|k, p) = \binom{k + i - 1}{i} \cdot p^k \cdot (1 - p)^i\)P(i|k,p) =⎛
   ⎜
   ⎝k + i − 1
   i⎞
   ⎟
   ⎠ · pk
   · (1 − p)i
   The value represents the number of failures in a series of independent yes/no trials
   (each succeeds with probability p), before exactly k successes occur.
   std::negative_binomial_distribution satisfies 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
   p returns the distribution parameters
   k (public member function)
   (C++11)
   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>
 #include <string>
 int main()
 {
     std::random_device rd;
     std::mt19937 gen(rd());
     // Pat goes door-to-door selling cookies
     // At each house, there's a 75% chance that she sells one box
     // how many times will she be turned away before selling 5 boxes?
     std::negative_binomial_distribution<> d(5, 0.75);
     std::map<int, int> hist;
     for (int n = 0; n != 10000; ++n)
         ++hist[d(gen)];
     for (auto [x, y] : hist)
         std::cout << std::hex << x << ' ' << std::string(y / 100, '*') << '\n';
 }

Possible output:
 0 ***********************
 1 *****************************
 2 **********************
 3 *************
 4 ******
 5 ***
 6 *
 7
 8
 9
 a
 b

External links
   Weisstein, Eric W. "Negative Binomial Distribution." From MathWorld — A Wolfram Web
   Resource.