generate random numbers (no member generate exist error)

Question

I'm trying to create an object that is supposed to implement some methods for my roulette program, but when compiling I got error that no member generate exist in std::random_device

here is a class example:

#include <random>
class Engine
{
public:
    Engine();

    int spin();
private:
    std::mt19937 m_generator;
    std::uniform_int_distribution<int> m_distribution;
    std::random_device m_seed;
};


Engine::Engine() :
    m_generator(m_seed),
    m_distribution(0, 36)
{
}

int Engine::spin()
{
    return m_distribution(m_generator);
}

// now let's try it out

Engine eng;

for(int i = 0; i < 20; ++i)
    eng.spin();

what am I doing wrong?

the above code opens a std header with code that is not easy to understand

Answer 1

The engine std::mt19937 requires a seed in its constructor. You are passing it an std::random_device. It looks like you intended to do something like

Engine::Engine() : m_generator(m_seed()), m_distribution(0, 36) {}
                                     ^^

You should also make sure m_seed has been initialized before it is used. This will require declaring it before m_generator:

private:
    std::random_device m_seed;
    std::mt19937 m_generator;
    std::uniform_int_distribution<int> m_distribution;

although I suspect you don't really need that member, and you can say

Engine::Engine() : m_generator(std::random_device()()), 
                   m_distribution(0, 36) {}

See this live example.