Lab 3, Overloading Operators in C++

Goals for this lab

By the end of this lab you should be comfortable with operator overloading in C++. Additionally you will gain experience in separating implementation from interface by using .h files for class declarations (the interface) and .cpp files for the definitions (implementation).

Pairing Reminder

You must work as a pair on the labs. If you were paired up last week, you need to work with the same pair. If you did not get paired up last week, or your pair is no longer in the class, please see the TA.

Lab Preparation

Change into the cs32 directory, and create a lab directory:

cd cs32
mkdir lab3

Change into the lab3 directory and copy files you will need for this lab:

cd lab3
cp ~cs32/public_html/code/lab3/* .

Building a Vec3 class

You are provided with the files Makefile, main.cpp, and vec.h. In this lab, you will need to add all the functionality that main.cpp expects from the Vec3 class. You will have to both, declare new functions in vec.h and write the corresponding implementation in vec.cpp.

Step 1: Add the constructors

You will need to declare and define the two constructors. This will allow you to build the program main by running make.

Step 2: Add the getters and setters

Next you will need to define the getters and setters for x, y and z. Once you have done that, comment out the appropriate lines in main.cpp to verify you have correctly done the implementation. You will need to complete step 3 before being able to test the setters.

Step 3: Overload << for cout

In this step you will need to overload the << operator such that it outputs Vec3 objects like so:

( x, y, z )

Of course, x, y, and z should be replaced with their double values. Again, when this step is completed, uncomment the next set of lines in main.cpp to verify this functionality works.

Step 4: Overload >> for cin

A Vec3 object should be created when cin >> some_vec3_object is contained in a C++ program. You don’t need to do any fancy verification of double input. Simply read directly into the three doubles that the Vec3 instance contains. Again, uncomment additional lines in main.cpp to test this functionality.

For convenience, you can run your program via the following command to avoid having to retype the numbers each time:

echo "0.1 0.2 0.3 1.8 2.7 3.6" | ./main

Step 5: Overload + for adding two Vec3 instances

Now you will need to overload + so that you can add two Vec3 instances. Think about what the parameters should be and what the return value should be. Vec3 objects should be added by adding their individual components together. For instance Vec3(1, 2, 3) + Vec3(4, 5, 6) should produce Vec3(5, 7, 9). Test this functionality as previously described.

Step 6: Overload * for multiplying a Vec3 instance by a double

Finally, you will need to overload * so that you can multiple a Vec3 by a double. When multiplying a Vec3 by a double, each component of the Vec3 should be multiplied by the value of the double. For instance Vec3(1, 2, 3) * 4 should produce Vec3(4, 8, 12).

To test this uncomment the remaining lines in main.cpp. By now you should be able to successfully run the complete main.cpp program. Given the command listed in step 4, main should produce the following output:

Individual components of 3-param: 5.5 6.6 7.7
From default constructor: ( 0, 0, 0 )
From 3-param constructor: ( 5.5, 6.6, 7.7 )
Input three doubles: Updated using setters: ( 0.1, 0.2, 0.3 )
Input three doubles: Updated using >> overloading: ( 1.8, 2.7, 3.6 )
The previous two added together: ( 1.9, 2.9, 3.9 )
More addition: ( 3.8, 5.8, 7.8 )
Simple multiplication: ( 0.8, 1.6, 2.4 )
More multiplication: ( 0.6, 1.2, 1.8 )

Submission Instructions

Please make only one submission per pair; this isn’t essential, it just makes life easier for the TA.

~cs32/submit lab3@cs32 vec.cpp vec.h

You may submit up to 20 times. Please check the feedback email to ensure you submitted correctly, and are satisfied with your final score. If you are not, feel free to revise and submit again. Please also review the automated feedback instructions as needed.


Template design by Andreas Viklund