Walking through a relatively basic C++ Template

Question

Our instructor has asked us to walk through a Template and explain what the various pieces of it are doing:

Template<class T> set<T> set<T>:: setDifference(const Set<T> &that) const

Here is what I've got so far:

Template<class T>: declares the new template

set<T>: states the return type of our template

set<T>: pretty confused about the second set, possibly the class name?

setDifference: Calls on our setDifference function

const Set<T> &that: 
Parameters of setDifference, states set<T> cannot be modified within                          
setDifference or put on the left hand side of the equation. "&that" references "that"     
memory location to use/call

const (at the end): 
Our function can only be called by a const object of the class
nor can it call any non-const member functions or change member variables. 

If anyone could please correct/add to what I already have I would greatly appreciate it.

Answer 1

It's the beginning of the definition of the member function setDifference outside of its class body

template <class T>
struct set{
//...
    set setDifference( const set& that) const;
};
template<class T>
set<T> set<T>::setDifference( const set<T>& that) const
{
    set<T> newInstance (...);
    //implementation of setDifference: newInstance = this - that
    return newInstance;
}

• The return type is a newly created instance of the set class
• The second set is indeed the class name; needed because setDifference lives in the namespace set<T>
• you're right about the rest