Poisson Probability Mass Function in C++

main.cpp

#include <iostream>
#include <iomanip>
#include "math.h"

using namespace std;

float pmf(int k, double lambda) {
    // https://en.wikipedia.org/wiki/Poisson_distribution#Definition
    return pow(M_E, k * log(lambda) - lambda - lgamma(k + 1.0));
}

int main(int argc, const char * argv[]) {
    // insert code here...
    cout << "Given a 50% female ratio, probability of 6 out of 6 girls at bus stop is "
        << setprecision(3)
        << pmf(6.0, 3.0) * 100.0
        << "%" << endl;
    return 0;
}