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Michael Drinkwater

CoWeb Assignment 1
CoWeb Assignment 2
CoWeb Assignment 3


"Nil illegitimum carborundum."



CoWeb Assignment 1:

Implement a method in Squeak that will give you the nth Fibonacci number. For both 0 and 1, the Fibonacci number equals 1. From then on, the next in the series is simply the sum of the previous two in the series (1, 1, 2, 3, 5, 8, 13, 21, 34, 55, etc.). Return an error when applicable. Your code should be based on good OO-style and be an efficient algorithm.

There are two basic methods of implementing the Fibonnaci Sequence: iteration and recursion. First, the long way, iteration:

    fibIterative: num
       "This method calcutes the nth Fibonacci's number using iteration."
       | a b c |
       (num < 0) ifTrue: [^self error: 'Non-negative integers only.'].
       (num < 2) ifTrue: [^1].
        a _ 1.
        b _ 1.
       2 to: num do: [:i |
           c _ a + b.
           a _ b.
           b _ c.].
       ^c

Pretty straight forward, slower than the other method though, recursion:

    fibRecursion: num
       "This method calcutes the nth Fibonacci's number using recursion."

       (num < 0) ifTrue: [^self error: 'Non-negative integers only.'].
       (num < 2) ifTrue: [^1]
           ifFalse: [^(self fibRecursion: (num - 1)) + (self fibRecursion: (num - 2))].


The following code solves the rainfall problem, which you may have seen in previous CS classes. For each line, describe what the Smalltalk code does. Be as specific as possible. In particular, what is data at the various points in the code?

| data onlyPositiveNumbers |
The two temporary variables, data and onlyPositiveNumbers are declared (but not initialized) in this line.
data := OrderedCollection withAll: #(1 2 3 -4 -5 'error' 6 -7 999 2).
Initializes the variable data as an OrderedCollection with the values given within the parentheses.
Note: the value 'error' is a string, unlike the rest of the values, which are numbers.
onlyPositiveNumbers := [:i | (i isKindOf: Number) and: [i positive]].
Initializes the variable onlyPositiveNumbers as a block (of code).
This paticular block tests the class and values of whatever it is used on.
data := data select: onlyPositiveNumbers.
Reassigns data to the values within itself that satisfy the block onlyPositiveNumbers.
Strangely enough, these values are the entries with data that are numbers greater than zero.
The variable data is now composed of 1, 2, 3, 6, 999, 2.
data := data copyUpTo: 999. "not including"
Reassigns data to a non-inclusive copy of data, stopping at the value 999.
The variable data is now composed of 1, 2, 3, 6.
Note: the code "not including" doesn't do anything, this is a comment.
Transcript show: data average
Calculates the average of the entries in data and prints it to the Transcript.
The sum of the entries is 12, and the displayed average is 3.



CoWeb Assignment 2:

Monticello: How do we use Monticello to manage group code?

Monticello is a built in component of Squeak that allows you to easily acess a repository. This guide will guide you through using Monticello one step at a time, including creating a repository.

Step 1: Creating a repository...
Monticello does not support the creation of a repository, that must be done on your own. The Monticello browser supports 4 primary types of repositories:
Note that Squeak supports 4 other repository types. However, one of the listed four will probably be the most convenient to use. In this walk-through, we will be using an HTTP repository. While you could set up your own site if you wanted, there is a very easy to use site already dedicated to this purpose.

Visit this site and create a user-name and a project: http://www.squeaksource.com

Step 2: Adding the repository to the Monticello browser...
After having created your repository, open the Monticello browser by red-clicking (that's a left-click for most of you) in the world and going to the open option. A little over half-way down, you should see the listing: Monticello Browser.

Now click the +Repository button (circled in red) on the top of the browser window and choose the HTTP option from the pop-up window. You should see this:

Uploaded Image: monticello.JPG

In the prompt, enter in the information for the location and username/password of the repository you created. You should now see a listing for it in the browser window.

Step 3: Adding a package to the repository...
Now, click the +Package button on the left and enter the name of the package you wish to work on with other team members. The package name shold now appear in the left window. Now select both the package name (on the left) and the repository name (on the right) and click the Save button. This adds the package to the repository where it can be downloaded by yourself and other people. This is also the button you use to commit your changes.

Step 4:Loading a package from the repository...
Select the desired repository and click the Open button on the right. This brings up a new window with all the packages inside the repository. You can see all the revisions and thier comments to each package by selecting them. Select the package and version you wish to load in, and click the Load button. Should you hapen to break your project and not be able to fix it, not an all together unlikely occurence, repeat these steps to replace your current code with the working code from the repository.

Step 5: Merging changes and submitting...
If you're an adventurous type person (like me), or if you just plain don't like your group members, you can skip to the next paragrpah. For those of you left: after you've finished whatever it is you wanted to do, go back to the Monticello browser and open the repository again. Select the package you've been working on and find the latest version of it. Sometimes the numbering can get messed up within the file names, so it's best to right click in the right window and select unchanged. This reorganizes the versions to match their order in the repository regardless of file name. For most systems, this puts the version in chronological order. Now, find and click the merge button and Squeak will bring up a window detailing all the changes it's about to load in. Take a careful look at these and ensure that they don't correspond to any of the methods you've been working in before continuing the merge.

If you've just skipped the last paragraph, I congratulate you and wish you a merry time among your soon to be angry group members. Go to the Monticello main browser window and select the package you wish to commit (it's marked by an asterisk). Now highlight the repository on the right and click the Save button. This brings up a window where you can enter a comment. Keep in mind that these comments are actually viewable, unlike the ones no one can ever find in regualr old CVS. It is also worth noting (for those of you who skipped the last paragraph) that is possible to change the filename in the upperwindow to include someone else's initials, or, for the truly sadistic, the version number as well.



CoWeb Assignment 3:

Garbage Collection:
(Part A) What are the advantages and disadvantages to using garbage collection?
(Part B) Explain how reference counting works. Include an example.
(Part C) Explain how mark and sweep works. Include an example.
(Part D) What problems of garbage collection do generational scavenging and “stop and copy” address? How do they address them?

History of Object-Oriented Programming:
Pick two of the following four people and briefly describe one of their main contributions to object-oriented programming and design: Kent Beck, Ward Cunningham, Alan Kay, and Ivan Sutherland. (Note: Do not describe more than two.)

Ward Cunningham invented the first wiki, WikiWikiWeb. In addition, he also worked with Kent Beck to come up with the first CRC cards. He was also a pioneer in design patterns and Extreme Programming. The wiki is a website that is both viewable and editable within an internet browser. This site is a type of wiki. Another example of a wiki is http://www.wikipedia.org.

Ivan Edward Sutherland's most noticable achievment is the invention of Sketchpad. It changed the way people interacted with computers, and basically kicked off the ideas of computer-aided-drafting (CAD) and computer graphics. Sketchpad was essentiall ythe first GUI and it led to the beginnings of object-oriented programming.

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