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std::geomet...distribution(3)  C++ Standard Libary std::geomet...distribution(3)

NAME
     std::geometric_distribution - std::geometric_distribution

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

	Produces  random non-negative integer values i, distributed according to
     discrete
	probability function:

	\(P(i|p) = p \cdot (1-p)^i\)P(i|p) = p A. (1 a p)i

	The value represents the number of failures in a series  of  independent
     yes/no trials
	(each succeeds with probability p), before exactly 1 success occurs.

	std::geometric_distribution<>(p) is exactly equivalent to
	std::negative_binomial_distribution<>(1,  p).  It  is  also the discrete
     counterpart of
	std::exponential_distribution.

	std::geometric_distribution satisfies RandomNumberDistribution.

Template parameters
		  The result type generated by the generator. The effect is  un-
     defined 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	RandomNumberDis-
     tribution.

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  p	distribution parameter (probability of a
     trial
	(C++11)       generating true)
		      (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
	std::geometric_distribution<>(0.5)  is	the  default  and represents the
     number of coin
	tosses that are required to get heads.

     // Run this code

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

      int main()
      {
	  std::random_device rd;
	  std::mt19937 gen(rd());

	  std::geometric_distribution<> d;
	      // same as
	      // std::negative_binomial_distribution<> d(1, 0.5):

	  std::map<int, int> hist;
	  for (int n = 0; n != 10000; ++n)
	      ++hist[d(gen)];

	  for (auto [x, y] : hist)
	  {
	      const char c = x < 10 ? x + '0' : x - 10 + 'a';
	      std::cout << c << ' ' << std::string(y / 100, '*') << '\n';
	  }
      }

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

External links
	Weisstein, Eric W. "Geometric Distribution." From MathWorld a A  Wolfram
     Web
	Resource.

http://cppreference.com 	   2024.06.10	   std::geomet...distribution(3)
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