Question

Can i have a class

Class Room{ ~Room(); virtual cost()
=0; }

Class Hotel{ map<int, Room> rooms; /*
*/ };

will my hotel become abstract ?
Can it hold the list of concrete Room objects that are derived from Room ?

Answer 1

The code you have written is not valid C++. If you mean:

class Room{ 
   ~Room();
   virtual int cost() =0; 
};

then yes, the class is abstract. You cannot then create a map like this:

map <int, Room> rooms;

but you can like this:

map <int, Room *> rooms;

Then assuming you have a class SingleRoom that is derived from Room and implements cost(), you can say:

rooms.insert( make_pair( 101, new SingleRoom ) );

Also, please note that abstract classes must have virtual destructors.