C++11: Random number generator in a class

Question

This question has been solved! The key is to use {} initiation instead of using (). So change it to std::normal_distribution<> rnorm{0,1}; although you may see many old online examples still using ().

I was thinking to generate random normal with a fixed seed for reproducible research. To illustrate my question well, I made the following minimalist codes. It reports error when I put the random generator in a class. What's wrong with the first code block? How can I fix it? Many thanks for your help!

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

class RandNorm{
private:
    unsigned seed = 12345;
    std::default_random_engine generator(seed);
    std::normal_distribution<> rnorm(0,1);

public:
    double getrnorm(){
    return rnorm(generator);
    }

};

int main() {
  RandNorm x;
  cout << x.getrnorm() << endl;
  return 0;
}

But it works well it I just put in in the main function as below

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

int main() {

    unsigned seed = 12345;
    std::default_random_engine generator(seed);
    std::normal_distribution<> rnorm(0,1);

    for(int i=1; i<10; i++){
        cout << rnorm(generator) << endl;
    }

 return 0;
}

from that code i would expect an error like "geta() not declared" — 463035818_is_not_an_ai, Mar 22 '17 at 16:51
it should be getrnorm(). Just updated the codes a little. It reported that seed is not defined in the class. — drbombe, Mar 22 '17 at 16:51
/testcpp.cpp|8|error: unknown type name 'seed'| /testcpp.cpp|9|error: expected parameter declarator| — drbombe, Mar 22 '17 at 16:53
Also related: http://stackoverflow.com/questions/11490988/c-compile-time-error-expected-identifier-before-numeric-constant. Short answer: use constructor initialization lists or brace-initialization e.g. `std::default_random_engine generator{seed};` and `std::normal_distribution<> rnorm{0,1};`. For the second, the default args are `0` and `1`, so `std::normal_distribution<> rnorm;` should work just fine. — vsoftco, Mar 22 '17 at 16:56

C++11: Random number generator in a class

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