Set constructors & destructors

Syntax:

    #include <set>
    set();
    set( const set& c );
    ~set();

Every set has a default constructor, copy constructor, and destructor.

The default constructor takes no arguments, creates a new instance of that set, and runs in constant time. The default copy constructor runs in linear time and can be used to create a new set that is a copy of the given set c.

The default destructor is called when the set should be destroyed.