random_distributions.cpp

//C++ 11 onwards
//Historgram Playground commented at bottom
#include <random>
#include <iostream>
 
int main()
{
    std::random_device rd;  //Will be used to obtain a seed for the random number engine
    std::mt19937 gen(rd()); //Standard mersenne_twister_engine seeded with rd()
    
    //Various range distributions
    std::uniform_int_distribution<> dis(1, 6);
    std::uniform_real_distribution<> dis(1.0, 2.0);
    
    std::geometric_distribution<> d; // same as std::negative_binomial_distribution<> d(1, 0.5);
    
    // if particles decay once per second on average,
    // how much time, in seconds, until the next one?
    std::exponential_distribution<> d(1); //This is the continuous counterpart of geometric_distribution
    
    // values near the mean are the most likely
    // standard deviation affects the dispersion of generated values from the mean
    std::normal_distribution<> d{5,2}; //5 is mean, dispersion from mean is at range +/-2
    
 
    for (int n=0; n<10; ++n)
        //Use dis to transform the random unsigned int generated by gen into an int in [1, 6]
        std::cout << dis(gen) << ' ';
    std::cout << '\n';
}

/*
int main()
{
    std::random_device rd;
    std::mt19937 gen(rd());
    // perform 4 trials, each succeeds 1 in 2 times
    std::binomial_distribution<> d(4, 0.5);
 
    std::map<int, int> hist;
    for (int n = 0; n < 10000; ++n) {
        ++hist[d(gen)];
    }
    for (auto p : hist) {
        std::cout << p.first << ' '
                  << std::string(p.second/100, '*') << '\n';
    }
}
*/