<random>

<random> provides random number engines (std::mt19937, std::random_device) and distributions (std::uniform_int_distribution, std::normal_distribution). Engine and distribution are separate to allow reusing an engine with different distributions.

Always seed with a good entropy source: std::random_device() for unpredictable values, or a fixed seed for reproducibility.

This example generates a random die roll and a normally-distributed random value using different distributions with the same engine.

// compile: g++ -std=c++11 -o randomexample randomexample.cpp
// run: ./randomexample
// description: random integers and normal distribution
 
#include <random>
#include <iostream>
 
int main() {
    std::mt19937 gen(std::random_device{}());
    std::uniform_int_distribution<int> dist(1, 6);
 
    std::cout << "die roll: " << dist(gen) << "\n";
 
    std::normal_distribution<double> normal(0.0, 1.0);
    std::cout << "normal: " << normal(gen) << "\n";
 
    return 0;
}