Assignments

Homeworks will come fast and furious at first, then you'll move on to work in a project. Feel free to talk with other people about the homeworks. However, there will be tests and quizes based on the material in the homeworks, so if you don't do the work, you will do poorly. In fact, it is good to do your homework with a partner. You learn more with a partner, and you might spend less time. If you do a homework with someone else, just submit one solution and put both your names on it. Make
sure that you are doing equal amounts of work. If your partner is doing most of the work, get another partner or you won't learn as much.

Send in all homeworks to cs497@chip.cs.uiuc.edu by 10:30 a.m. of the day it is due. Do NOT use attachments. Include all code by pasting it into your message. If you use attachments then we will end up with hundreds of little files, mostly with the same name. This makes it hard to tell which file is yours. Make the subject of your message by "homework 1", "homework 2", and so on. This will help us keep them separate if you are ahead of schedule. You can go as fast as you want, but we
probably will hand back your homeworks along with everybody else's.

Many students have asked questions about the homeworks and have had them answered on the swiki. Take a look at these questions before you start a homework, and feel free to ask more questions. The homeworks change a little each semester, and we try to edit the questions to keep up with the changes, but sometimes we make mistakes.

Again these schedules that I have mentioned here are tentative. Please look out for any changes in them.

•     hw1 - Aug 27 - Do all exercises in the first 6 chapters of Hopkins and Horan. These chapters and exercises are all easy, so this is sort of a warm up for the later homeworks. Even so, this is a lot of material, and I estimate it will take you 5-10 hours to work through it all. Note that none of the exercises require you to send us anything until chapter 5. Send us (by e-mail) the results of exercises 5.14, 6.3, the files you created as exercise 6.12 and 6.13. What is the result of  evaluating (using "print it") the expression "100 factorial"?

        Also, go to the class wiki and make an entry for yourself under the "list of people". Introduce yourself, explain why you want to take this class, and leave your e-mail address.

•     hw2 - Sep 1 - Read chapters 7-9 of Hopkins and Horan. This is 35 pages. Do the exercises in chapter 7, sending us the results of 7.6, 7.8, and 7.9.

    Pay close attention to the hint of 7.9. The problem is that some methods don't return what you expect. In particular, "x at: 3 put: 'third'" will not return x. However, "x at: 3 put: 'third'; yourself" will return x.

    Do the exercises in chapter 8, sending us the results of 8.3 and 8.4. 8.5 is optional. Do the exercises in chapter 9 too, but don't send us anything.

    Get the source code for the Payroll example that we did in class. Check the Employee class and the three subclasses of EmployeeTransaction to see whether they are using the proper pattern for initializing objects. In other words, whether  there is a "complete creation method" as a class method and an "instance initialization method" as an instance method. If not, fix them, and report what you changed.

    Write a script that simulates the following. Write it in a workspace. Keep adding to it little by little. Read the code to figure out the exact syntax for anything you don't know how to do. Note that the class method "test" of PayrollSystem is a lot like this. Send in the script for the following:

    John Doe was hired May 1, 1999. His initial salary was $20 an hour. He turned in his time-card on May 5 and had  worked 40 hours. He worked 40 hours the week of May 12, too. He received a pay-check on May 15. What was his take-home pay?

•     hw3 - Sep 3 - read chapter 10-13. It is very important to learn to find things in the class library. These exercises will  help teach you that. They require looking around with the browser. So, you need to learn to find the implementation of a  method with a particular name (use "find implementors"), the variables defined by a class, and so on. Smalltalk has    excellent tools for this, but you can't use them until you learn them. Do the exercises in 10 and send the results to us.

    Explain the results of 11.1, 11.2. Do 11.5. Make a method in Date that subtracts a number of days from an instance of  Date. What should it be called? What protocol should it be in? (Hint, find the method that adds a number of days to a Date.) File out that method and hand in the code. Do 12.4, 12.6, 12.7, 12.8, 12.11 (show us the code for Foo), 13.3, 13.4, 13.5, 13.9, and 13.13. Where is Rectangle's implementation of the "new" method? (This might be harder than you  think!) Smalltalk is ideal for experimentation. If you want to know whether something will work, just try it!
•     hw4 - Sep 8 - read chapter 22 and 23 on debugging, do the military rank homework.

•     hw5 - Sep 10 - read chapters 14 and 15. Do exercise 15.2. A binary tree is a collection that is made up of a set of nodes.

    Each node has two children and a value. The value stored in a node is greater than or equal to the values of its  right-most child or any of its children. The value stored in a node is less than or equal to the values of its left-most child or any of its children. The trick is to note that each node is itself a binary tree, so you only need to make one class, BinaryTree, which is also the class of your nodes. Make your binary tree class a subclass of Collection, not Object, and
implement do:. Note that do: should evaluate the block only for the values of the nodes, not the nodes themselves. The binary tree should then be able to understand size, addAll:, and inject:into:. Test it to make sure. It might be able to understand collect: and select:. If it doesn't, explain why not. Do the collection homework

    The payroll system doesn't handle vacation. Class Employee has a variable defined for it, and each time-card collects  the amount of vacation time that was taken that week, but the code for processing time-cards doesn't do anything about vacation.

    Change the payroll system to record the amount of vacation time that has been taken and the vacation time that has accrued. Assume that for every 50 hours of non-overtime that an employee works, they get 2 hours of vacation time. You should not need to add any more instance variables to any classes. You could do this by adding to accrued vacation  (hours worked / 25) - hours of vacation taken. Note that this will lead to fractional hours of vacation accumulated. This  might be a problem if this were being written in COBOL, but it is OK for Smalltalk.

    To find where the work gets done, try single-stepping through the posting of a time-card. Place a halt to start the debugger, and then single-step from there. You'll have to figure out how to get the hours of vacation taken and the hours worked. They are stored in the time-card.
 

•     hw6 - Sep 15 - Read chapters 16, 17, and 18. Do the Money exercise. Note that Money is really a double-dispatching exercise.

•     hw7 - Sep 17 - Do the streams homework.

•     hw8 - Sep 22 - read chapters 21, 24, and 27, Change Employee to use ValueWithHistory to store values that change over time. You won't use it to store the name of the Employee or its set of transactions, but you can use it for just about everything else. This will permit old transactions to work correctly even if a salary change or something similar has occurred.

    You will have to change the initialization method to initialize the Employee properly. Then you'll have to change everyplace you read the variable to use #at:, everyplace you assign to the variable to use #starting:become:, and everyplace you increment the variable to use #at:add:.

    Define a method for Employee called salaryHistoryOn: aStream. It prints a report on aStream that gives the dates of all salary changes and what the new salary was. The report should look something like

        January 15, 1975: $2.00 July 15, 1975: $2.10 January 15, 1976: $2.30 July 15, 1976: $2.50

    Do NOT hand in the entire payroll example. Just hand in your changes. We do not want to run your program, we want it  to be so clear that we can read the changes and tell that it is correct.
 

•     hw9 - Sep 24 - read chapters 19, 20, 28. Do 19.5, 19.6, 20.6, 20.9, 28.6, 28.8 and do the withholding homework for the payroll system.

•     hw10 - Sep 29 - read chapters 29 and 30. Read the patterns Strategy, Decorator, and Composite from the Design Patterns book. For each pattern, describe a place where you have seen the pattern in the homeworks or in the Smalltalk image. Do 30.8-30.13.

•     hw11 - Oct 1 - read chapters 31-33. Do 32.1-32.14 and 32.21. Read the patterns Observer and Template Method. For each pattern, describe a place where you have seen the pattern.

    - Learn the VisualWorks GUI builder. There is a VisualWorks tutorial for VW2.5 that is available in pdf. But since  there isn't one for VW3.0, perhaps they think that sections 17-23 in the Advanced Developers Guide (look in your "doc" directory) should be enough. Also, if you haven't found a class project, get one soon!
 
•     hw12 - Oct 8 - The last homework! Build a GUI for the payroll system. If I go too slowly through the GUI lectures,  you can wait til I'm done. Read Adaptor, Mediator and Interpreter. For each pattern, describe how the VisualWorks GUI  framework uses the pattern.

• Oct 13 - You should have chosen your project by now. Make sure there is a page on the class wiki that describes your project, and that you are listed as one of the members of that project.

• Oct 15 -Look at the best practice patterns by Ron Jeffries.

• Oct 27 - First demo. You should be ready to give a 15 minute demo of what you have done so far and to describe the problem you are solving and your current design. Also, you should have some sort of schedule for the rest of the semester that describes the tasks you have left, how long you think they will take, and who will do them. You are not required to follow this schedule, but it is good to think about it to make sure that you aren't trying to do too much.

• Nov 17 - Second demo. You should be ready to give a 15 minute demo of what you have done so far and to describe the problem you are solving and your current design.

• Dec 10 - Public demo. Some of you will give demos in class. Let me know by Wednesday (Dec. 8) whether your group will give a demo.

Final presentation of projects will be the week of finals through December 21.