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std::geomet...distribution(3) C++ Standard Libarystd::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  (1  p)i

	  The  value represents	the number of failures in a series of indepen-
       dent 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
       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  RandomNum-
       berDistribution.

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  Wol-
       fram Web
	  Resource.

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

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