Question

I have a class structure which is

template<int T>
class MyClass {
public:
    MyClass(){};
    ~MyClass(){};

    template<class K> void foo();
};

Now I want to specialize the foo() method based upon the value of the integer used in MyClass<int>, for instance if int the code we have MyClass<2> I want to use a different version of foo<K>() to if I had MyClass<3>. However I want to still have foo<K>() unspecialized on K.

So that would mean something like this would be okay

MyClass<2> myc2;
MyClass<3> myc3;
myc2.foo<SomeClass>();
myc2.foo<SomeOtherClass>();
myc3.foo<SomeClass>();
myc3.foo<SomeOtherClass>();

Is it possible to specialize in this way but not specialize on K? I’ve tried a few combinations with no success.

Answer 1

If I understood your question correctly, this is what you want:

template<int T>
class MyClass {
public:
    MyClass(){};
    ~MyClass(){};

    template<class K> void foo();
};

template<int T>
template<class K>
void MyClass<T>::foo()
{
    std::cout << "general form\n";
}

template<>
template<class K>
void MyClass<2>::foo()
{
    std::cout << "MyClass<2>\n";
}

int main()
{
    MyClass<3> c1;
    c1.foo<int>(); // general form
    MyClass<2> c2;
    c2.foo<int>(); // MyClass<2>
    c2.foo<float>(); // MyClass<2>
}