random always returns same values

[cCj]

Hi
I was trying to use the new c++ random classes but for some reason the output of the program is always the same. I tried to put Sleep() in there to make difference but the output remains the same.

#include <iostream>
#include <string>
using namespace std;
#include <random>
#include <functional>

#include <Windows.h>

int main()
{
std::default_random_engine generator;
std::uniform_int_distribution<int> distribution(2, 5);

auto dice = std::bind(distribution, generator);

Sleep(1000);

cout << dice() << " " << dice() << " " << dice() << endl; // output: 4 4 2


 return 0;
}

Output is: 4 4 2

Anyidea whats wrong?

[MiiNiPaa]

You did not seed your RNG.

std::default_random_engine generator( std::random_device{}() );

[cCj]

Thank you

[MiiNiPaa]

Additionally I would not suggest to use default_random_engine : it is usually implements a bad RNG. Use std::mt19937 for pretty good mersenne twister generator.

[cCj]

can I also ask what is the std::random_device{}() syntaxt about? I've never seen {} being used like that before.

[MiiNiPaa]

I create a temporary object of type std::random_device by using uniform initialization: std::random_device{}. Then I call operator() on that temporary object: std::random_device{}()

[cCj]

Ok makes sense, thanks