About the System: In version 6 of DukeDisc, the array of Slot objects is replaced with a doubly-linked circular data structure.

The Driver: You must write a driver named Driver6.cpp (that must be in the DukeDisc directory). The only difference between this driver and Driver5.cpp is that it must #include v6 of the DiscChanger class. Specifically:

#include "v6/DiscChanger.h"
#include "v5/TextInterface.h"
  

The Slot Class: You must create version 6 of the Slot class which must be in directory v6. In version 6 the Slot class will play the role of a "node" (actually, an exogenous node) in a linked data structure. This can be illustrated as follows:

Note that your Slot class can include other attributes in addition to the two Slot pointers and the char pointers illustrated above.

The constructor in the Slot class will need to be changed accordingly. It may not be necessary to make any other changes to the Slot class. (Indeed, the functionality of the Slot class must not be changed.)

The DiscChanger Class: You must create version 6 of the DiscChanger class which must be in directory v6. Version 6 must use a doubly-linked circular structure of Slot objects in place of the array used in version 5.

You will almost certainly need to change the implementation of the next() and previous() methods, and the destructor. You must change the constructors [or the method(s) that they call to perform common construction tasks] in such a way that it/they construct the linked data structure.

The linked data structure has to be constructed using an iterative process. Suppose, for example, you are constructing a DiscChanger that contains three Slot objects. Initially, the linked structure can be illustrated as follows:

Note that in these illustrations, the Slot pointers actually "point to" the entire Slot even though they might appear to point to a component.

When the next Slot is added, the linked structure can be illustrated as follows:

When the final (in this case, third) Slot is added, the linked structure can be illustrated as follows:

Of course, the actual size of the linked data structure will be determined by the size parameter passed to the explicit value constructor.

Hint: First create a doubly-linked linear structure in a loop. Then, outside of the loop, connect the first and last Slots. When creating the linear structure, think about using a point to the first Slot, a pointer to the last Slot, and a pointer to the Slot being added.

Using friend Classes: You may want to list the DiscChanger class as a friend in the Slot class.

How to Proceed: Of course, how you proceed is up to you. However, it is fairly easy to make disastrous mistakes when working with pointers so you should be very careful. One possible approach follows.

Starting with pencil and paper:

1. "Hard code" the construction of the linked structure for a specific number of slots (e.g., four).
2. Write and test next() and previous().
3. Write and test the destructor.
4. Write and test the iterative process for constructing the linked structure.
5. Re-test next(), previous(), and the destructor.

Now start typing, following the steps described above.

While it seems like this will take a long time, any other approach will almost certainly take much longer.

Building: The following makefile may prove to be useful in this regard:

# Phony target to build all versions
#
all: v1 v2 v3 v4 v5 v6

# Phony targets for each version
#
v1: Driver1
v2: Driver2
v3: Driver3
v4: Driver4
v5: Driver5
v6: Driver6

# Drivers
#
Driver1: Driver1.o v1/DiscChanger.o v1/Slot.o
	g++ Driver1.o v1/DiscChanger.o v1/Slot.o -o Driver1

Driver1.o:  Driver1.cpp v1/DiscChanger.h
	g++ -c Driver1.cpp

Driver2: Driver2.o v2/TextInterface.o v1/DiscChanger.o v1/Slot.o
	g++ Driver2.o v2/TextInterface.o v1/DiscChanger.o v1/Slot.o -o Driver2

Driver2.o:  Driver2.cpp v2/TextInterface.h v1/DiscChanger.h 
	g++ -c Driver2.cpp

Driver3: Driver3.o v2/TextInterface.o v3/DiscChanger.o v1/Slot.o
	g++ Driver3.o v2/TextInterface.o v3/DiscChanger.o v1/Slot.o -o Driver3

Driver3.o:  Driver3.cpp v2/TextInterface.h v3/DiscChanger.h 
	g++ -c Driver3.cpp

Driver4: Driver4.o v2/TextInterface.o v3/DiscChanger.o v1/Slot.o
	g++ Driver4.o v2/TextInterface.o v3/DiscChanger.o v1/Slot.o -o Driver4

Driver4.o:  Driver4.cpp v2/TextInterface.h v3/DiscChanger.h 
	g++ -c Driver4.cpp

Driver5: Driver5.o v5/TextInterface.o v5/DiscChanger.o v5/Slot.o
	g++ Driver5.o v5/TextInterface.o v5/DiscChanger.o v5/Slot.o -o Driver5

Driver5.o:  Driver5.cpp v5/TextInterface.h v5/DiscChanger.h 
	g++ -c Driver5.cpp


Driver6: Driver6.o v5/TextInterface.o v6/DiscChanger.o v6/Slot.o
	g++ Driver6.o v5/TextInterface.o v6/DiscChanger.o v6/Slot.o -o Driver6

Driver6.o:  Driver6.cpp v5/TextInterface.h v6/DiscChanger.h 
	g++ -c Driver6.cpp


# v1 of DiscChanger and Slot
#
v1/DiscChanger.o: v1/DiscChanger.cpp v1/DiscChanger.h v1/Slot.h
	g++ -c v1/DiscChanger.cpp -o v1/DiscChanger.o

v1/Slot.o: v1/Slot.cpp v1/Slot.h
	g++ -c v1/Slot.cpp  -o v1/Slot.o



# v2 of TextInterface
#
v2/TextInterface.o: v2/TextInterface.cpp v2/TextInterface.h
	g++ -c v2/TextInterface.cpp -o v2/TextInterface.o



# v3 of DiscChanger
#
v3/DiscChanger.o: v3/DiscChanger.cpp v3/DiscChanger.h v1/Slot.h
	g++ -c v3/DiscChanger.cpp -o v3/DiscChanger.o



# v5 of DiscChanger, Slot and TextInterface
#
v5/DiscChanger.o: v5/DiscChanger.cpp v5/DiscChanger.h v5/Slot.h
	g++ -c v5/DiscChanger.cpp -o v5/DiscChanger.o

v5/Slot.o: v5/Slot.cpp v5/Slot.h
	g++ -c v5/Slot.cpp  -o v5/Slot.o

v5/TextInterface.o: v5/TextInterface.cpp v5/TextInterface.h
	g++ -c v5/TextInterface.cpp -o v5/TextInterface.o


# v6 of DiscChanger and Slot
#
v6/DiscChanger.o: v6/DiscChanger.cpp v6/DiscChanger.h v6/Slot.h
	g++ -c v6/DiscChanger.cpp -o v6/DiscChanger.o

v6/Slot.o: v6/Slot.cpp v6/Slot.h
	g++ -c v6/Slot.cpp  -o v6/Slot.o
  

You can build version 6 of DukeDisc with the command make v6.

Testing: Make sure you thoroughly test your code. Thing about the kinds of things you needed to test for in PA2 and what additional kinds of things you need to test for now.