Array operations with array of structs

[Peter via Digitalmars-d-learn]

Hi,
I have a struct with arithmetic operations defined using opBinary 
but array operations with arrays of it don't work.

struct Vector3 {
     public double[3] _p;
     ...
     Vector3 opBinary(string op)(in Vector3 rhs) const
     if (op == "+"){
         Vector3 result;
         result._p[] = this._p[] + rhs._p[];
         return result;
     }
     ...
}

unittest{
     auto a = Vector3([2.0, 2.0, 0.0]);
     auto b = Vector3([1.0, 2.0, 1.0]);
     Vector3[] c = [a];
     Vector3[] d = [b];
     Vector3 e = a + b; // works
     Vector3[] f;
     f[] = c[] + d[]; // Error: invalid array operation 'f[] = c[] 
+ d[]' because Vector3 doesn't support necessary arithmetic 
operations
}

how can I get this to work?

Thanks