Computer Science City College of New York
CSc21200 Data Structures,
Fall 2009
Programming Assignment 3: Revise the sequence Class to
Use a
Dynamic Array (Chapter 4)
Modified from projects of Chapter 4 at
www.cs.colorado.edu/~main/projects/
of Data Structures and Other Objects Using C++ by Michael Main and Walter
Savitch
- The Assignment:
- You will implement and test a revised sequence class that uses a
dynamic array to store the items.
- Purposes:
- Ensure that you can write a small class that uses a dynamic
array as
a private member variable.
- Before Starting:
- Read all of Chapter 4.
- Due Date:
- Wednesday, Oct 07,
2009. If you have problems,
late work will be accepted on Friday with no penalties. Late work may
be submitted
on Saturday or Sunday with 5% penalty per day. No work will be accepted
after
Sunday.
- How to Turn In:
- Pack your files in a WinZip file (Windows) or tar
file (Unix). Attach the file in your email with "CSC212 Assignment 3"
in your message Subject line, send it to Wai Khoo ( WKhoo@gc.cuny.edu
)
- Files that you must write and turn in (Please do not turn in
other files!!):
- sequence2.h: The header file for the new sequence
class. Actually, you don't have to write much of this file. Just start
with our version and add your name and
other information at the top. If some of your member functions are
implemented as inline functions, then you may put those implementations
in this file too. By the way, you might want to compare this header
file with your first sequence header file (sequence1.h)
. The new version no longer has a CAPACITY constant because
the items are stored in a dynamic array that grows as needed. But there
is a DEFAULT_CAPACITY constant, which provides the initial size
of the array for a sequence created by the default constructor.
- sequence2.cxx: The implementation file for the new
sequence class. You will write all of this file, which will have the
implementations of all the sequence's member functions.
- Other files that you may find helpful (but you do not needto
turn in):
- sequence_test.cxx:
This is in fact the same interactive test program that you used with
the earlier sequence. If you want to use it with the new sequence, then
copy it to your directory and open it with your editor. Then change the
statement
#include "sequence1.h"
to
#include "sequence2.h"
And change the statement
using namespace main_savitch_3
to
using namespace main_savitch_4
- seq_ex2.cxx: A
non-interactive test program that will be used to grade the correctness
of your new sequence class.
The sequence Class Using a Dynamic Array
Discussion of the Assignment
Your sequence class for this assignment will differ from the your
previous sequence in the following ways:
- The number of items which may be stored in the sequence should
only be limited by the amount of memory available on the heap. When new
items are added to a sequence which is at capacity, the size of the
data array in
which items are stored should be automatically enlarged.
- Because you are dynamically allocation memory within your
sequence class, you will need to define a copy constructor, an
assignment operator, and a destructor.
- The constructor should have a default argument which allows the
user to set the initial capacity of the sequence.
- There should be a resize function that allows the user to
explicitly set the the capacity of the sequence.
Start by declaring the new sequence's private member variables in
sequence2.h. This should include the dynamic array (which is declared
as a pointer to a value_type). You will also need two size_type
variables to keep track
of the number of items in the sequence and the total size of the
dynamic
array. After you've declared your member variables, write an invariant
for
the top of sequence2.cxx.
Many of the features of this class are similar to the bag
class from Section 4.3, so start by thoroughly reading Section 4.3 and
pay attention to new features such as how the sequence differs from a
bag (see page 119). Also the implementation of some of the functions
are almost the same as
in Part 1. Once again, do your work in small pieces. For example, my
first
version of the sequence had only a constructor, start, insert, advance,
and
current. My other member functions started out as stubs.
Use the interactive test program and the debugger to track down
errors in your implementation. If you have an error, do not start
making changes until you have identified the cause of the error.
The ability to initialize and use a static member constant within
the class definition is a relatively new feature. If you have an older
compiler (for example, Visual C++ 6.0) that does not
support static const members, then you may use
enum {DEFAULT_CAPACITY = 30};
instead of
static const size_type DEFAULT_CAPACITY = 30;
After this definition, the name bag::DEFAULT_CAPACITY is
defined to have the integer value 30. Although this is not the intended
use of
an enum definition, the result is the same as using a static member
constant (see more discussions at page 99 in the textbook).
When a member functions needs to increase the size of the dynamic
array, it is a good idea to increase that size by at least 10% (rather
than by
just one item).
The sequence Class Using a Dynamic Array
*Optional Part of the Assignment (for extra 10% points )
You may wish to provide some additional useful member functions, such
as
(1) Operators + and +=.. For + operator, x+y contains all the items of
x, followed by all the items in y. The statement x += y appends all the
items in y to the end of what's already in x.
(2) Operator []. For a sequence x, we would like to be able to refer to
the individual items using the usual C++ notation for arrays. For
example, if x has three items, then we want to be able to write x[0],
x[1] and x[2] to access these three items. The use of the square
brackets is called the subscript operator. The subscript operator may
be overloaded as a member
function, with the prototype shown here as part of the sequence class:
class sequence
{
public:
...
value_type operator[](size_type index) const;
...
};
The only parameter is the index of the item we want to retrieve. The
implementation of this member function should check that the index is
valid, and then return the specified item.
Zhigang Zhu
( zhu@cs.ccny.cuny.edu ),
2009