Question

I currently have the following non templated code:

class Vector{ 
  public:
    double data[3];
 };
static Vector *myVariable;
void func() {
  myVariable->data[0] = 0.;
}
int main() {
  myVariable = new Vector();
  func();
}

I then want to template the dimension :

template<int DIM> class Vector{ 
  public:
    double data[DIM];
 };
static Vector<3>* myVariable;
void func() {
  myVariable->data[0] = 0.;
}
int main() {
  myVariable = new Vector<3>();
  func();
}

But I finally want to template my variable as well, with the dimension :

template<int DIM> class Vector{ 
  public:
    double data[DIM];
 };
template<int DIM> static Vector<DIM> *myVariable;

void func() {
  myVariable->data[0] = 0.;
  // or perform any other operation on myVariable
}
int main() {
  int dim = 3; 

  if (dim==3)
    myVariable = new Vector<3>();
  else
    myVariable = new Vector<4>();

  func();
}

However, this last version of the code produces an error : this static variable cannot be templated (“C2998: Vector *myVariable cannot be a template definition”).

How could I possibly correct this error without a complete redesign (like inheriting the templated Vector class from a non templated class, which would require more expensive calls to virtual methods , or manually creating several myVariables of different dimensions) ? Maybe I’m just tired and don’t see an obvious answer :s

Edit: Note that this code is a minimal working code to show the error, but my actual implementation templates the dimension for a full computational geometry class, so I cannot just replace Vector by an array. I see that there doesn’t seem to be a solution to my problem.

Thanks!

Answer 1

I think I found!

template<int DIM> class Vector{ 
  public:
    double data[DIM];
 };
static void *myVariable;

template<int DIM>
void func() {
((Vector<DIM>*)myVariable)->data[0] = 0.;
  // or perform any other operation on myVariable
}
int main() {
  int dim = 3; 

  if (dim==3)
  {
    myVariable = (void*) new Vector<3>();
    func<3>();
  }
  else
  {
    myVariable = (void*) new Vector<4>();
    func<4>();
   }


}