Reference

<random>

public member function
<random>

std::geometric_distribution::operator()

(1)
template<class URNG>result_type operator()(URNG& g);
(2)
template<class URNG>result_type operator()(URNG& g, const param_type& parm);
Generate random number
Returns a new random number that follows the distribution's parameters associated to the object (version 1) or those specified by parm (version 2).

The generator object (g) supplies uniformly-distributed random integers through its operator() member function. The geometric_distribution object transforms the values obtained this way so that successive calls to this member function with the same arguments produce values that follow a geometric distribution with the appropriate probability.


Parameters

g
A uniform random number generator object, used as the source of randomness.
URNG shall be a uniform random number generator type, such as one of the standard generator classes.
parm
An object representing the distribution's parameters, obtained by a call to member function param.
param_type is a member type.

Return value

A new random number.
result_type is a member type, defined as an alias of the first class template parameter (IntType).

Example

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// geometric_distribution example
#include <iostream>
#include <chrono>
#include <string>
#include <random>
int main()
{
 // construct a trivial random generator engine from a time-based seed:
 int seed = std::chrono::system_clock::now().time_since_epoch().count();
 std::default_random_engine generator (seed);
 std::geometric_distribution<int> distribution (1.0/5);
 std::cout << "each star is 5 spaces away from the next (on average):" << std::endl;
 for (int i=0; i<100; ++i) {
 int number = distribution(generator);
 std::cout << std::string (number,' ') << "*";
 }
 return 0;
}

Possible output:
each star is 5 spaces away from the next (on average):
 * * * ** * * * * * ** *
* * * * * * * * * * ** *
* * * * * * * * **** * ** * **
 * ** * * * * * * ** * * * *
 *** * * * * * * * * * * ** ***
 * *** * ** * * ** * * *
 * * * * * * ***


Complexity

Amortized constant (a constant number of invocations of g.operator()).

See also

geometric_distribution::param
Distribution parameters (public member function)

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