Project 4
Inheritance and Polymorphism
with Shapes

Assigned March 31, 2003
Design Due Sunday April 6, 2003, 11:59pm
Program Due Sunday April 13, 2003, 11:59pm
Updates 03 April 2003, 3:40pm
A couple of students have asked if it's okay to have a vector of Shape pointers for each different type of Shape, or is it a requirement to have just one vector of Shape pointers (that gets passed to DrawShapes().
You are required to have only one vector of Shape pointers.
Here's why...one reason is practical, the others are just good design
  1. One measure of how good a program design is is its extensibility. That means how well can this program handle changes to the type of inputs, and/or the range of inputs and/or other similar unforseen situations.
    A program that has one vector of Shape pointers for each type of shape will require more modifications than a program with just one vector of shape pointers when a new shape is added to the input file and is therefore less extensible and therefore a poorer design.
  2. Having a vector of Shape pointers for each type of shape means that there's no real need for the shapes to have an identity, or at least no need for your code to use the identity, since the vector determines the type and therefore the identity, making DrawShapes() potentially less polymorphic.
  3. On the practical side, we desire that your program "draw" shapes in the same order in which they were read from the input file. This is only possible if only vector of shape pointers is used.
  • 01 April 2003, 4:40pm
    A couple of students asked whether it was okay to check for invalid data such as a negative radius in main() when the file is being read. Yes, that's generally a good idea, but.....
    1. As the implementer of a class, you cannot depend on the user of your class to verify their data. Therefore, good defensive programming dictates that your class should check the data anyway.
    2. To gain experience with exceptions in this project, you need to construct ill-formed shapes.
    So, bottom line -- don't validate the input in main(), but rather construct the shapes regardless of the data and let the member functions throw exceptions.

    • Objectives

    Project Description

    In this project, you will reuse code from projects 2 and 3 (your Point class), implement classes already designed for you, and you will design and implement derived classes based on their descriptions below.

    In this project you will also create exception classes to be thrown by some of your class' methods and caught by their callers.

    The various shape classes are shown in the inheritance heirarchy diagram below.

    Shape, Circle and Rectangle (and their associated exception classes) have defined for you in their respective .H files found in Mr. Frey's public directory for this project. You may not change these files. Although you may wish to copy these files temporarily to your working directory, your makefile should reference these files and they should not be submitted.

    In this project, you will read information about various shapes from an input file, instantiate new shapes with the required attributes, and then "draw" all the shapes using a polymorphic function. Your main( ) should perform the usualy command line argument verification, open the input file, read the shape information from the file, instantiate each shape and then print all the shapes. Be sure to delete any and all dynamically allocated memory so there are no memory leaks.
    The command line will have just one argument -- the name of the input file.

    Class Definitions

    The Shape Class

    The Shape class is an abstract class which is at the top of the inheritance heirarchy. It is defined for you in Shape.H in Mr. Frey's public directory. You may not change this file. You must implement the Shape class in Shape.C.

    The Circle Class

    The Circle class is derived from the Shape class. It is defined for you in Circle.H in Mr. Frey's public directory. You may not change this file. You must implement the Circle class in Circle.C. Note that the Circle class has a private data member for PI. Intialize this data member to 3.14159.

    The Rectangle Class

    The Rectangle class is derived from the Shape class and defined in Rectangle.H in Mr. Frey's public directory. You may not change this file. You must implement the Rectangle class in Rectangle.C

    The Cylinder Class

    A cylinder is a 3-dimensional object with a circular base and "sides" which are perpendicular to the base. Its 3rd dimension is the length of the sides, usually known as it's height. The Cylinder class should be (and must be) derived from the Circle class. You must design and implement the Cylinder class. It's definition will be in Cylinder.H and it's implementation in Cylinder.C.

    The Ring Class

    A ring is a 2-dimensional shape formed by two concentric circles with different radii. The picture below shows a ring. The area of the ring is represented by the shaded portion of the picture. The Ring class should be (and must be) derived from the Shape class. You must design and implement the Ring class. It's definition will be in Ring.H and it's implementation in Ring.C.

    The Sphere Class

    A sphere is a 3-dimensional circle (a ball). In addition to the area and circumference of the underlying circle, the sphere also has volume and surface area. The Sphere should be (and must be) derived from the Circle class.

    The Point Class

    The Circle and Rectangle classes both use Point objects in their definition. You should reuse your Point class from project 2 or project 3. Note that Circle.H and Rectangle.H both #include Point.H so it may be necessary to rename your file.

    The Polymorphic Function

    After the file has been read and all shapes have been created, you must use the polymorphic function DrawShapes( ) to "draw" all of the shapes your project has created. All shapes are created, then all are "drawn" You cannot use this function to draw one shape at a time.
    Since we cannot actually draw shapes, we will interpret "draw" to mean "print out relevant information about the shape". This "relevant information" is described below in the     sample output section.

    The prototype for this function is void DrawShapes( const vector< const Shape* >& shapePtrs); and cannot be changed. This function may be included in Proj4.C

    Exceptions

    Each shape has a method to draw itself and/or one or more methods which performs a calculation. For example, the Circle class provides a method for calculating its area and another for calculating its circumference. Each of these methods requires that the radius of the circle be positive, otherwise the circle is not well formed. When methods such as these detect an ill-formed shape, these methods should throw an exception to be caught by the caller.

    Exception classes for the Circle and Rectangle classes have been defined for you. Use them as a model for exception classes for your shapes.

    It is not necessary to throw exceptions from your constructors.

    The Input File

    The input file will contain one line of data for each shape to be created. The data items on each line will be separated by one or more spaces. The file may contain blank lines.

    If a line is not blank, you may assume that the data is in the correct order and that each data item is of the appropriate type as described below.

    The first data item on each line will be the type of shape to create. The data item will be one of the following (without the quotes), all in lowercase -- "circle", "cylinder", "rectangle", "ring", "sphere"

    The remaining data items on the line will depend on the shape type.

    1. If the shape type is circle or sphere the remaining data items are
      1. integer x-coordinate of the center
      2. integer y-coordinate of the center
      3. floating point radius
    2. If the shape type is cylinder the remaining data items are
      1. integer x-coordinate of the center
      2. integer y-coordinate of the center
      3. floating point radius
      4. floating point height
    3. If the shape type is rectangle the remaining data items are
      1. integer x-coordinate of the lower left corner
      2. integer y-coordinate of the lower left corner
      3. integer x-coordinate of the upper right corner
      4. integer y-coordinate of the upper right corner
    4. If the shape type is ring the remaining data items are
      1. integer x-coordinate of the center
      2. integer y-coordinate of the center
      3. floating point inner radius
      4. floating point outer radius

    Sample Output

    The sample output below was produced by processing the file named proj4.dat found in Mr. Frey's public directory. Although your output does not have to match exactly, the following output requirements must be met and all data fields shown below must be present.
    1. All floating point values must be output with 4 decimal places and right justified in a field of 10 characters. This should cause the decimal places to align nicely.
    2. Points must be formatted as in projects 2 and 3; i.e. enclosed in parenthesis with coordinates separated by commas.
    3. All labels must be followed by a colon. All colons must be vertically aligned.
    4. All output must be labelled with the shape's type.
    5. All headings must be underlined as shown in the sample output All characters in the heading must be underlined and there may be no extraneous underlining. The following are NOT acceptable.

      This is my heading           This is my heading
      -----------                    ------------------------
    linux1[5]% Proj4 p4.dat I am a Circle ------------- Center : ( 3, 4 ) Radius : 2.6500 Area : 22.0618 Circumference: 16.6504 I am a Rectangle ---------------- Upper Left: ( 1, 7 ) UpperRight: ( 4, 7 ) Lower Left: ( 1, 2 ) LowerRight: ( 4, 2 ) Length : 3.0000 Width : 5.0000 Area : 15.0000 Perimeter : 16.0000 I am a Circle ------------- Circle with radius -42.0000 is ill-formed I am a Cylinder --------------- Center : ( 3, 4 ) Radius : 4.7000 Area : 69.3977 Circumference: 29.5309 Volume : 249.8318 I am a Ring ----------- Inner Circle ------------ Center : ( 2, 3 ) Radius : 2.7000 Area : 22.9022 Circumference: 16.9646 Outer Circle ------------ Center : ( 2, 3 ) Radius : 5.4000 Area : 91.6088 Circumference: 33.9292 Ring Area : 68.7066 I am a Sphere ------------- Center : ( 4, 5 ) Radius : 2.6500 Area : 22.0618 Circumference: 16.6504 Volume : 77.9517 Surface Area : 88.2473 linux1[6]%

    Hints, Suggestions and Free advice

    1. Mr. Frey's public directory for this project is
      /afs/umbc.edu/users/d/e/dennis/pub/CMSC202/proj4
    2. Use incremental development
      1. Implement the Circle and Rectangle classes first. Write test program to exercise their methods.
      2. Write main( ) and DrawShapes( ) and make them work for Circles and Rectangles.
      3. Implement the Cyclinder class. Write a test program to exercise all the methods. Then add Cylinders to main( )
      4. Implement the Ring class. Write a test program to exercise all its methods. Then add Rings to main
      5. Add exceptions to your code. Keep the exception classes a simple as possible.
    3. Use a simple approach to reading the file. Using getline( ) is NOT recommended. A simple approach also makes EOF detection easier.
    4. Review the makefile for project 1 to see how to reference .H files in Mr. Frey's public directory.
    5. Visit the discussion board
    6. To be sure your class' destructors are being called, temporarily put an output statement in each one. Be sure to remove this output statement before submitting your project.
    7. Use 3.14159 for the value of PI so your answers will match those
    8. The area of a circle = PI * radius2. It's not necessary to use the pow( ) function.
    9. The circumference of a circle = 2 * PI * radius
    10. The volume of a cylinder = area of base * height
    11. The volume of a sphere is 4/3 * PI * radius3
      Note that 4 / 3 is NOT the same as 4.0 / 3.0.... which should you use?
    12. The surface area of a sphere is 4 * PI * radius2

    Project Design Assignment

    Your project design document for project 4 must be named design4.txt. Be sure to read the     design specification carefully. Submit your design in the usual way. submit cs202 Proj4 design4.txt

    Project Make File

    You are required to submit a make file with this project. The grader should simply need to type "make Proj4" and your project should compile and link to an executable called Proj4. The grader should also have the ability to do a "make clean" and "make cleanest."
    Hint: Start with the makefile from project 1 and modify it as necessary.

    See the make tutorial for more help on make and makefiles.

    Project Grading

    The grade for this project will be broken down as follows. A more detailed breakdown will be provided in the grade form you recieve with your project grade. This list should not be considered comprehensive, but rather a suggested list of things you should consider before turning in your project.

    85% - Correctness -- 85%

    1. Have you correctly used inheritance to define your classes?
    2. Have you properly reused code from the base class?
    3. Are all appropriate member functions "virtual"?
    4. Are all appropriate member functions "const"?
    5. Are all return values being returned in the appropriate way (by value, by reference, by const reference)?
    6. Are all function parameters being passed into the function in the appropriate way (by value, by reference, by const reference)?
    7. Does your output meet all output requirements?
    8. Are all calculated values correct?
    9. Have you properly implemented DrawShapes( )?
    10. Do all appropriate functions have the proper PreConditions? If so, are all PreConditions handled?
    11. Are you throwing exceptions wherever required?
    12. Are all exceptions being caught and handled properly? I.e. being thrown by the appropriate methods, caught by the caller and dealt with appropriately?

    15% - Coding Standards

    Your code adheres to the CMSC 202 coding standards as discussed and reviewed in class.

    Project Submission

    You should submit the following files.

    DO NOT SUBMITShape.H, Circle.H or Rectangle.H

    Submit as follows:

    submit cs202 Proj4 <list of files> A complete guide to submit tools is available on the course website.

    More complete documentation for submit and related commands can be found here.

    Remember -- if you make any change to your program, no matter how insignificant it may seem, you should recompile and retest your program before submitting it. Even the smallest typo can cause compiler errors and a reduction in your grade.