How to specialize template member functions in template class (already specilzied)?

问题

For example:

template<unsigned number>
struct A
{
    template<class T>
    static void Fun()
    {}
};

template<>
struct A<1>
{
    template<class T>
    static void Fun()
    {
       /* some code here. */
    }
};

And want to specialize A<1>::Fun()

template<>
template<>
void A<1>::Fun<int>()
{
    /* some code here. */
}

doesn't seem to work. How to do it? Thanks.

回答1:

An explicit specialization of a class template is like a regular class (it is fully instantiated, so it is not a parametric type). Therefore, you do not need the outer template<>:

// template<> <== NOT NEEDED: A<1> is just like a regular class
template<> // <== NEEDED to explicitly specialize member function template Fun()
void A<1>::Fun<int>()
{
    /* some code here. */
}

Similarly, if your member function Fun were not a function template, but a regular member function, you would not need any template<> at all:

template<>
struct A<1>
{
    void Fun();
};

void A<1>::Fun()
{
    /* some code here. */
}

来源：https://stackoverflow.com/questions/17503697/how-to-specialize-template-member-functions-in-template-class-already-specilzie