← Patterns

Flip a biased coin

12345678910#include <random> int main() { std::random_device random_device; std::mt19937 random_engine{random_device()}; std::bernoulli_distribution coin_distribution{0.25}; bool outcome = coin_distribution(random_engine); }

This pattern is licensed under the CC0 Public Domain Dedication.

Requires c++11 or newer.


Generate a random boolean value according to a bernoulli distribution.


The std::random_device on line 5 provides a source of uniform non-deterministic random numbers (where such a source is available). We use this to seed the Mersenne Twister random number engine, std::mt19937, on line 6. Consider other random number engines for different properties.

On line 7, we create a std::bernoulli_distribution representing a bernoulli distribution with a success probability of 0.25. This can be thought of as a biased coin that will land on heads only a quarter of the time.

Finally, we generate a random number from the random engine, distributed according to the bernoulli distribution (line 9). This gives us a boolean value that will be true with 0.25 probability and false otherwise.


  • Joseph Mansfield

Last Updated

09 December 2017


Fork this pattern on GitHub