std::default_random_engine generates the same values even with changing seed?

Question

I'm trying to implement a class that will serve as sort of a wrapper for the random library so I can use its objects and functions in (I think) a more intuitive way elsewhere in my code. In my header I have something like this: ``` class RandomDevice{ private: unsigned long rand_seed; default_random_engine engine; public: RandomDevice(unsigned long n); int randInt(int min, int max);}; ``` And then in the .cpp file I implement those two functions (constructor and `randInt`) like so: ``` RandomDevice::RandomDevice(unsigned long n){ rand_seed = n; default_random_engine engine; engine.seed(n); } int RandomDevice::randInt(int min, int max){ uniform_int_distribution<int> distribution(min, max); return distribution(engine); } ``` Finally, in my `main.cpp` I test these functions like this: ``` int main(){ unsigned long seed = 1; RandomDevice my_rand(seed); cout << "random integer: " << my_rand.randInt(0, 10) << endl; } ``` The problem is, no matter what I set the seed to in `main.cpp`, I alwa…

Accepted Answer

```
default_random_engine engine;
engine.seed(n);
```

This is seeding the local `engine`, which is destroyed at the end of the constructor, not the class member `engine`, which ends up being default constructed.

Use the member initializer list instead:

```
RandomDevice::RandomDevice(unsigned long n) : rand_seed(n), engine(n){ }
```

std::default_random_engine generates the same values even with changing seed?

Solution

Problem