public member function
<random>
| (1) | explicit exponential_distribution ( result_type lambda = 1.0 );
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| (2) | explicit exponential_distribution ( const param_type& parm ); |
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Construct exponential distribution
Constructs an exponential_distribution object, adopting the distribution parameters specified either by lambda or by object parm.
Parameters
- lambda
- Average rate of occurrence (λ).
This represents the number of times the random events are observed by interval, on average.
Its value shall be positive (λ>0).
result_type is a member type that represents the type of the random numbers generated on each call to operator(). It is defined as an alias of the first class template parameter (RealType).
- parm
- An object representing the distribution's parameters, obtained by a call to member function param.
param_type is a member type.
Example
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// exponential_distribution example
#include <iostream>
#include <chrono>
#include <thread>
#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::exponential_distribution<double> distribution (1.0);
std::cout << "ten beeps, spread by 1 second, on average: " << std::endl;
for (int i=0; i<10; ++i) {
double number = distribution(generator);
std::chrono::duration<double> period ( number );
std::this_thread::sleep_for( period );
std::cout << "beep!" << std::endl;
}
return 0;
}
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Output:
ten beeps, spread by 1 second, on average:
beep!
beep!
beep!
beep!
beep!
beep!
beep!
beep!
beep!
beep!
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