Educational Objectives: After completing this assignment the student should have the following knowledge, ability, and skills:
Operational Objectives: Create the generic container class fsu::Queue<T> that satisfies the interface requirements given below, along with an appropriate test harness for the class.
Deliverables: Three files queue.t, fqueue.cpp, and log.txt.
builds: [1 pt each]
fqueue.x [student harness] x
fqueue_int.x x
fqueue_String.x x
in2post.x x
constTest.x x
tests: [5 pts each]
fstack_char.x b < s.com1 [0..5]: x
fstack_int.x b < s.com2 [0..5]: x
fstack_String.x b < s.com3 [0..5]: x
fqueue_char.x b < q.com1 [0..5]: x
fqueue_int.x b < q.com2 [0..5]: x
fqueue_String.x b < q.com3 [0..5]: x
in2post.x b < i2p.in1 [0..5]: x
in2post.x b < i2p.in2 [0..5]: x
constTest.x [0..5]: x
code quality [-50..0]: ( x)
dated submission deduction [2 pts each]: ( x)
--
total [0..50]: xx
An abstract data type, abbreviated ADT, consists of three things:
The operations and axioms together should determine a unique character for the ADT, so that any two implementations should be essentially equivalent. (The word isomorphic is used to give precision to "essentially equivalent". We'll look at this in the next course.)
The queue ADT is used in many applications and has roots that pre-date the invention of high-level languages. Conceptually, queue is a set of data that can be expanded, contracted, and accessed using very specific operations. The queue ADT models the "FIFO", or first-in, first-out rule. The actual names for the queue operations may vary somewhat from one description to another, but the behavior of the abstract queue operations is well known and unambiguously understood throughout computer science. Queues are important in many aspects of computing, ranging from hardware design and I/O to inter-machine communication and algorithm control structures.
Typical uses of ADT Queue are (1) buffers, without which computer communication would be impossible, (2) control of algorithms such as breadth first search, and (3) simulation modelling of systems as diverse as manufacturing facilities, customer service, and computer operating systems.
The queue abstraction has the following operations and behavior:
As one example of the use of ADTs in computing, consider the following function that illustrates an algorithm for converting arithmetic expressions from infix to postfix notation:
...
#include <queue.t>
#include <stack.t>
...
typedef fsu::Queue < Token > TokenQueue;
typedef fsu::Stack < Token > TokenStack;
// a Token is either an operand, an operator, or a left or right parenthesis
...
bool i2p (TokenQueue & Q1, TokenQueue & Q2)
// converts infix expression in Q1 to postfix expression in Q2
// returns true on success, false if syntax error is encountered
{
...
TokenStack S; // algorithm control stack
Q2.Clear(); // make sure ouput queue is empty
while (!Q1.Empty())
{
// take tokens off Q1 and use them to build Q2
// if syntax error is detected return false
}
return true;
} // end i2p()
This is a complex algorithm, but not beyond your capability to understand. The main points to displaying it here are: (1) to illustrate how stacks and queues may be used in implementing applications, and (2) to let you know that your code must be compatible with such apps. in2post.cpp is one of our tests!
We will implement the queue abstraction as a C++ class template Queue with the following public methods:
// Queue < T > API void Push (const T& t); // push t onto queue T Pop (); // pop queue and return removed element; error if queue is empty T& Front (); // return front element of queue; error if queue is empty const T& Front () const; // const version size_t Size () const; // return number of elements in queue bool Empty () const; // return 1 if queue is empty, 0 if not empty void Clear (); // make the queue empty void Display (std::ostream& os, char ofc = '\0') const; // output contents through os
There should be a full complement of self-management features:
Queue (); // default constructor Queue (const Queue&); // copy constructor ~Queue (); // destructor Queue& operator = (const Queue&); // assignment operator
Unlike Stack, Queue requires access to data at both the front and back, which makes an array implementation impractical. We will use a linked list implementation using a link class defined as follows:
class Link
{
Link ( const T& t ); // 1-parameter constructor
T element_;
Link * nextLink_;
friend class Queue<T>;
};
Note that all members of class Link are private, which means a Link object can be created or accessed only inside an implementation of its friend class Queue<T>. The only method for class Link is its constructor, whose implementation should just initialize the two variables. (This can be done inside the class definition, as shown below.)
The private Queue variables for this implementation will be exactly two pointers to links, the first and last links created. Including the definition of the helper class Link, the private section of the class definition should be like the following (with implementor-chosen private variable names):
template < typename T >
class Queue
{
public:
...
private:
class Link
{
Link ( const T& t ) : element_(t), nextLink_(0) {}
T element_;
Link * nextLink_;
friend class Queue<T>;
};
Link * firstLink_;
Link * lastLink_;
};
The class constructor will have responsibility for initializing the two variables to zero. These two pointers will be zero exactly when there is no data in the queue (the queue is empty). Links for data will be allocated as needed by Push() and de-allocated by Pop(). These operations will also need to re-direct appropriate link pointers in the dynamically allocated links, and maintain the class variables firstLink_ and lastLink_ correctly pointing to the links containing the first and last elements of the queue. The destructor should de-allocate all remaining dynamically allocated links in the queue. The Size() method will have to loop through the links to count them, whereas the Empty() method can do a simple check for emptiness of the queue.
Because this implementation relies on dynamically allocated memory, the container makes no restrictions on the client program as to anticipated maximum size of the queue.
Create and work within a separate subdirectory cop3330/proj8. Review the COP 3330 rules found in Introduction/Work Rules.
After starting your log, copy the following files from the course directory [LIB] into your proj8 directory:
proj8/in2post.cpp proj8/constTest.cpp proj8/deliverables.sh area51/in2post*.x area51/fqueue*.x scripts/submit.sh # not needed if you have set up "submit.sh" as a command in your ".bin"
The naming of these files uses the convention that _s are compiled for Sun/Solaris and _i are compiled for Intel/Linux. Use one of the sample client executables to experiment to get an understanding of how your program should behave.
Define and implement the class template fsu::Queue<T> in the file queue.t. Be sure to make log entries for your work sessions.
Devise a test client for Queue<T> that exercises the Queue interface for at least one native type and one user-defined type T. Put this test client in the file fqueue.cpp. Be sure to make log entries for your work sessions.
Test Stack and Queue using the supplied application in2post.cpp. Again, make sure behavior is appropriate and make corrections if necessary. Log your activities.
Turn in queue.t, fqueue.cpp, and log.txt using the submit.sh submit script.
Warning: Submit scripts do not work on the program and linprog servers. Use shell.cs.fsu.edu to submit projects. If you do not receive the second confirmation with the contents of your project, there has been a malfunction.
Queue should be a proper type, with full copy support. That is, it should have a public default constructor, destructor, copy constructor, and assignment operator. Be sure that you test the copy constructor and assignment operator.
The Queue constructor should create an empty queue with no dynamic memory allocation.
The Queue<T>::Push(t) operation must dynamically allocate memory required for storing t in the queue. Similarly, the Queue<T>::Pop() operation must de-allocate memory used to store the element being removed from the queue.
As always, the class destructors should de-allocate all dynamic memory still owned by the object. The stack and queue implementations will be very different.
Use the implementation plan discussed above. No methods or variables should be added to these class, beyond those specified above and in the implementation plan.
The Display(os, ofc) method is intended to output the contents through the std::ostream object os in front-to-back order. The second parameter ofc is a single output formatting character that has the default value '\0'. (The other three popular choices for ofc are ' ', '\t' and '\n'.) The implementation of Display must recognize two cases:
Thus, for example, q.Display(std::cout) would send the contents of q to standard output.
The output operator should be overloaded as follows:
template < typename T >
std::ostream& operator << (std::ostream& os, const Queue<T>& q)
{
q.Display (os, '\0');
return os;
}
The overload of operator <<() should be placed in your queue header file immediately following the class definition.
The class Queue should be in the fsu namespace.
The file queue.t should be protected against multiple reads using the #ifndef ... #define ... #endif mechanism.
The test client program fqueue.cpp should adequately test the functionality of queue, including the output operator. It is your responsibility to create this test program and to use it for actual testing of your queue data structure.
Your test client can be created by making very small changes in a copy of fstack.cpp you created as part of the preceding assignment.
Keep in mind that the implementations of class template methods are in themselves template functions. For example, the implementation of the Queue method Pop() would look something like this:
template < typename T >
T Queue<T>::Pop()
{
// yada dada
return ??;
}
We will test your implementation queue.t using (1) our test client fqueue.cpp and (2) in2post (with our stack implementation).
There are two versions of Queue::Front(). These are distunguished by "const" modifiers for one of the versions. The implementation code is identical for each version. The main point is that "Front()" can be called on a constant queue, but the returned reference may not be used to modify the front element. This nuance will be tested in our assessment. You can test it with two functions such as:
char ShowFront(const fsu::Queue<char>& q)
{
return q.Front();
}
void ChangeFront(fsu::Queue<char>& q, char newFront)
{
q.Front() = newFront;
}
Note that ShowFront has a const reference to a queue, so would be able to call the const version of Front() but not the non-const version, but that suffices. ChangeFront would need to call the non-const version in order to change the value at the front of the queue. A simple test named "constTest.cpp" is posted in the distribution directory.