Question

To be honest, I do not really know how to name that problem. I’ll just show the code that is not working:

template<int SIZE>
struct bar{

};

template<int SIZE>
struct foo{
    template<int X>
    void f(bar<X> b);
};

template<int SIZE, int X>
void foo<SIZE>::f(bar<X> b){

}


int main(){
    foo<1> f;
    bar<2> b;
}

I’d like to separate definition from implementation to avoid cyclic dependency issues. Separation is done in header files only, I don’t want to put template code into cpp files. Using pointers is no option in that case. Refactoring has been considered but is not a real option, either.

Implementing foo::f without a parameter that has template parameters itself is working fine. I do not really get the problem with that parameter, though.

Code should work using gcc 4.7 and (even more important) Visual Studio 2010. C++11 is ok as long as supported by the platforms mentioned.

Solutions, workarounds as well as theoretical explanations why I’m doing something completly wrong will be highly appreciated. TIA.

Answer 1

template<int SIZE, int X>    //problem : what is what here?
void foo<SIZE>::f(bar<X> b){

}

It is wrong syntax.

The correct syntax is to use template twice as:

template<int SIZE>   //for the class template
template<int X>      //for the member function template
void foo<SIZE>::f(bar<X> b){

}

Note that the order matters here.