Question

I am doing something that is probably silly, but it would be nice if it worked.

I am attempting to specialize types in a way that I need my own lookup structure that is essentially global (but ideally encapsulated as a class variable), but I want the objects to be type safe, so they are parameterized.

Consequently, I have, essentially

template<class T, int N>
class SpecialArray
{
//...
private:
   static map<string, internal_t> lookupTable
}

and for whatever reason, I didn’t think until such time as I went to initialize lookupTable
that when I say

template <class T, int N>
SpecialArray<T,N>::lookupTable;

there are going to be many different lookupTables running around attached to the various instantiations of SpecialArray.

I suspect it may just be a pipe dream and that the correct answer is just making it a separate global singleton object, but is there anyway to make it such that there is just one lookupTable for all the SpecialArrays?

Like, in the C++ in my mind (which is not real C++), this would go something like

template <class T, int N>
SpecialArray<*,*>::lookupTable;

… but sadly GCC does not compile the C++ in my mind

Is there any actual way to get what I want (somewhere in C++0x-land or something)? I am likely to run into this problem also with some static methods that manipulate this lookup table (which does not keep track of types or Ns).

… sorry if that didn’t make any sense.

Thanks in advance for any help or sympathy you can render.

Answer 1

You could add a non-templated base class and move lookupTable into that class:

class Base
{
protected:
    static map<string, internal_t> lookupTable
};

template<class T, int N>
class SpecialArray : Base
{
    //...
};