CPSC 225: Intermediate Programming
Spring 2007

Course Links

• Course Information

  (general information about the course, including assessment)

• Course Policies

  (course policies on attendance, collaboration, late/makeup work, and other things)

• Syllabus

  (syllabus, including links to handouts, assignments, reading material...pretty much everything you want on a daily basis is here)

• Course Wiki

  (discussion and journals) - on-campus access only

• Programming Standards

  (the C++ programming style/conventions used and expected in this class, as well as the grading criteria for programming assignments)

Unix Links

• Using Linux at HWS

  (lots of useful information about the Linux systems at HWS)

• CS124 Lab 1 (spring 2005)

  (basic Linux usage information - logging in, working with files and directories, printing)

Announcements

[4/17] Q: What's the threshold for figuring out if something is spam?

A: There is no threshold, exactly. From the handout:

• Specifically, the likelihood of an email being spam is computed as the difference between the message length and 100 (subtract 100 from the message length and take the absolute value), divided by the number of previously-seen emails (including the current one) with the same sender as the current one.

• You can implement a particular probability of something happening using rand() - the probability of the expression rand()%100 < k being true is k/100.

The idea is that if there's a 50% chance of something being spam, you could flip a coin to figure out if that message is spam - heads = spam, tails = not spam. But, certain properties increase or decrease the chance of something being spam, so that the probability of any given message being spam is not 50%. For example, maybe a given message has a 75% chance of being spam. So, you flip a coin which has a 75% chance of coming up heads, and declare the message to be spam if you get heads.

The formula for the likelihood is the calculation of what probability of heads your coin should have. The formula for taking an action with a certain probability (the one involving rand()) tells you how to use rand() to simulate flipping a coin with a given probability of heads.

[4/16] Q: "Continue reading emails until you get to the end of the file" pertains to the main program, and not necessarily having each e-mail received by an instructor read by the instructor?

A: Yes - "Continue reading emails" refers just to reading each message in from the file; it should then be received by the instructor. Whether or not it is ever actually read by the instructor is not something the main program worries about.

[4/15] Q: When do the instructors read their email?

A: They don't, at least not in this program.
You should support the ability of all instructors to read email, but the only time mail-reading will actually occur in this particular program is when a graduate student is coping.

[4/2] The original version of the WorldGUI class treats NORTH as being down; this is consistent with viewing north as increasing the row. If you done this, you're fine. If, instead, you have treated north as being up (and decreasing the row), you should copy the new version of worldgui.cc from /classes/s07/cs225/hw4/ to your directory so that north-facing creatures will point in the correct direction. This has the added advantage that the dirLeft and dirRight routines in geometry.h return directions which actually appear to be left and right turns.

Either interpretation of north (up or down) is acceptable, but you should make sure that you use the proper version of WorldGUI so that the creatures appear to move forward instead of backward.

[3/28] An issue that has come up a couple of times in Darwin's World:

Q: It keeps telling me that Species or World does not define a data type, even though I have included a header file that clearly indicates that Species and World DO define a data type.

A: You have circular #includes - world.h #includes species.h, and species.h #includes world.h. The error is because Species needs World and World needs Species - but which class declaration goes first?

The solution is to use a forward declaration of the class in one place. For example, remove #include "species.h" from World and replace it with

 class Species;

This forward declaration is like a forward declaration for a function - it announces to the compiler that "Species" is a class and should be treated as such. Then you don't need to #include "species.h" to get that information, and the cycle of #includes is broken.

Forward declarations won't solve every problem, however. Knowing that Species is a class is enough for the compiler to compile certain kinds of things (like Species parameters or variable declarations involving Species *) but isn't enough for other things (such as variable declarations involving Species objects or method calls) - for those you need to #include "species.h". This means that you'll likely need to #include "species.h" in world.cc (as the forward declaration of Species was only enough to compile the header file), and that it doesn't work to instead do a forward declaration of World in species.h (because Species has an instance variable of type World).

[3/22] Two corrections for the maze solver: when adding the adjacent rooms to the stack/queue of discovered rooms, only add rooms if they haven't been marked (the mark is NONE) and once added, mark them as discovered (not visited). The correct pseudocode:

    // ** while ( there are more discovered rooms ) {
    // **  choose a discovered room and remove it from the collection of
    // **   discovered rooms 
    // **  if it has been visited, continue with the next discovered room
    // **  otherwise {
    // **    mark it as visited in the GUI
    // **    if it is the exit, you're free (break out of the loop)
    // **    otherwise {
    // **      add the rooms adjacent to this room to the collection of
    // **       discovered rooms if not already visited or discovered
    // **      mark each as discovered in the GUI
    // **    }
    // **  }

    // pause briefly before repeating the loop, to slow down solving
    usleep(10000);                 

    // ** }

Also note that the usleep should go inside the while loop, as the last thing. This slows down the solving process a bit so you can watch it.

[3/2] A configuration file (unsurprisingly named config.txt) has been added to /classes/s07/cs225/hw4. If you've already copied the files to your directory, also copy the configuration file; if you haven't copied them yet, you'll get the configuration file along with everything else. This will let you run the Darwin's World demo.

[2/22] Two updates:

• I announced that programming assignment 4 would be posted today, but have decided to delay it to allow more time for covering material in class. It will be assigned next week instead. That means there is no programming assignment this week, just finishing the linked list lab.

• To accomodate the delay of programming assignment 4 and to avoid scheduling it over Passover and Easter, the second midterm has been pushed back two weeks to Friday 4/13 with the take-home part due the following Thursday. As this is well in future, I don't anticipate this change causing any difficulties - however, if it does, let me know as soon as possible.

[2/20, 2/21] A few clarifications on the take-home exam:

1. Don't name your executable "set". There's a builtin shell command named set, and your shell will try to run this one instead of your program. Choose a different (but still reasonable) name for your executable.

2. The input file containing the cards contains the full words ("PURPLE", "HASHED", etc); the short 4-letter card description is what is displayed on the screen to allow the user to play the game.

3. The example of the user entering 0 3 2 2 2 3 to specify a set is meant to be six separate numbers - a 0, a 3, a 2, a 2, etc. You do not have to somehow read everything as one unit and then try to split it up.

4. If there's something you don't know how to do, you can still test your program by substituting the part you don't know how to do with something else similar that you do know how to do. (Of course, you won't get credit for the thing you didn't do, but you can get credit for everything else.) The exam handout mentions doing this if you don't know how to read from a file as specified - prompt the user to enter the information from the keyboard instead. You can also do this for other aspects of the program e.g. if you don't know how to compute the short 4-letter card description, print out the full words instead (but still arrange them in the 3x4 grid).
   If there's something you can't quite get right, you can put the part that isn't quite right in comments to show how close you got and then implement an alternative so you can test the rest of your program. Just include a note about what you did so I can figure it out...

5. There will not be as significant a penalty for a non-compiling program as on the programming assignments. There will be deductions for syntax errors, but not an automatic 10% deduction (unless you have a *lot* of syntax errors). Thus, it is worth attempting to write something even if you aren't 100% on it.

6. You do not need to prevent a player from choosing the same set of cards more than once to score extra points. However, if you have done this, you don't need to remove it from your program.

[2/14] Q:

scrblgui.h:63: error: expected ',' or '...' before '&' token
scrblgui.h:63: error: ISO C++ forbids declaration of 'string' with no type

A: It doesn't know what string is. Where is string defined? Add the appropriate #include to scrblgui.h. It got left out and I got away with it in my version because of the order in which I did #includes elsewhere in the program.

[2/12] If you copied the scrbl files (scrblgui and the others for the bonus) from /classes/f06/cs225/hw3 as the handout said instead of noticing that the term should actually be s07, you should recopy them from /classes/s07/cs225/hw3 or else you will get compiler errors. The handout has been corrected.

[2/9] Make the following changes to landergame.cc:

• Change the calls to glutPostRedisplay() at the end of the step and keys functions to redraw().
• Remove the call to glutMainLoop() from main.

Make the following changes to landergui.cc:

• Change the line void step(); to void step ( int value );.
• Change the line glutIdleFunc(step); in the startGame function to glutTimerFunc(3,step,0);.

[1/23] Lab #2 and programming assignment #2 have been posted. Read the lab handout before coming to lab.

[1/23] Some general comments on lab #1 have been posted (see the syllabus page). The labs will be handed back in class on Wednesday.

[1/16] The course wiki is live! You can browse the content now. Thursday's lab will include some exercises to get you a little more familiar with the wiki. We'll also create accounts in lab on Thursday (please don't try to create one before then!) so you can view/edit your journal page and post comments.

[1/15] Welcome to CPSC 225! This web page is your source for a great deal of important and useful material, so you should take a few minutes to familiarize yourself with the website. Check back often for announcements and new information.

last updated: --Tue Apr 17 23:39:43 EDT 2007-- page owned by: bridgeman@hws.edu