Pass an array to an array member of undeclared size of a class

Question

I want to have an array whose values be declared from main to a class. Here's the sample code.

class test{
public:
      const double arr[];
};

int main(){

     test t;
     t.arr[] = {1, 2};
    return 0;
}

When I try to intialize in the main it gives me an error error:unexpected expression.

But if I remove the t.arr[] in main, it compiles fine.

Answer 1

1. const double arr[]; - variable length array? Invalid in C++.
2. t.arr[] - invalid syntax (operator[] call with no arguments?), arr is also const and you can't assign to any arrays.

But you can do aggregate intialization:

class test {
public:
    const double arr[2]; // fixed size
};

int main() {

    test t = {{1, 2}}; // not an assignment
    return 0;
}