C++: error “explicit specialization in non-namespace scope”

Question

template
class Bimap {
public:
    class Data {
    private:
        template Data& set(T);
        template<>         


        

Answer 1

One way forget templates, overload:

Data& set(T1 v) { /*...*/ }

but here is a trick which I use sometimes

you can specialize class template within class:

class {
    template<typename T>
    struct function_ {
        static void apply(T);
    };

    template<>
    struct function_<int> {
        ...
    };

    template<typename T>
    void function(T t) { return function_<T>::apply(t); }

Answer 2

@Albert

I had a similar problem when I wanted to add a "trim-excess-capacity" to a custom made container. The std::vector swap trick and changing the declaration of the existing container were not valid options. So I've come up with this:

template <class T, bool isPtr> struct DeleteImp
{
    static void Trim(T* to, unsigned int count);
};

template <class T> struct DeleteImp<T, false>       
{
    static void Trim(T* to, unsigned int count) {}
};

template <class T> struct DeleteImp<T, true>        
{
    static void Trim(T* to, unsigned int count)
    {
        for(unsigned int i=0; i<count; i++)
            delete to[i];
    }
};

used by my container like this:

DeleteImp<T, TypeTraits<T>::isPointer>::Trim(buf + length, truelength-length);

You may also want to check out this resource.