COM 3230: Object-Oriented Design

Frequently Asked Questions

Fall 1999

• Where can I find the Problem Set for this week??
  
  See www.ccs.neu.edu/course/com3230/index.html.
  
  
• Will the final exam cover all of the handout slides or just that you have talked in class?
  
  Formally, "all the material", for the simple reason that I don't necessarily remember what I said in class.. Practically, however, I will target at an exam that reflects what was taught.. even beyond the handouts.
  
  

  Winter 1999

• I was not able to attend your first class. Could you please send me syllabus of the course com3230 and handouts you handed to the class.
  
  All the course materials are available on-line. See www.ccs.neu.edu/course/com3230/index.html. The syllabus may be found in the Technicalities section.
  
  
• I just tried to access the lecture notes link on the course web site and I was denied access. However, I can get to the textbook and Smalltalk links.
  
  The notes are accessible only to CCS machines and only to students taking COM3230.
  
  
• I have problem in printing the lecture notes you showed in class. I first downloaded the ps files , and then printed them out, but the printout was garbage. could you show me some way that can print them out properly?
  
  The notes are provides in PostScript format "as is". I_ve tested them, and they printed fine using lpr -Pprinter_name notes.ps. If you have trouble, try first viewing them using ghostview and then printing them from within ghostview. You may also want to try a different printer. If you still cannot print them, come see me during office hours and I will print you a personal copy.
  
  
• I logged onto the computers at school and tried to execute the Smalltalk programs. I had no trouble finding the Smalltalk executable files (located in /course/com3230), but I can_t find the actual Smalltalk source files you mentioned in class. They are not located in this directory. I tried looking elsewhere, but I could not find these files. I really don_t want to have to use a web browser and pull down each of the files into my directory individually...is there an easier way I can gain access to the .st files from the school computers?
  
  The files are located in /course/com3230/.www/little
  
  
• The PC version of Smalltalk allows the backspace key to operate but on the Sun version, the backspace key produces the ^H sequence. My normal terminal settings have mapped this key to the backspace, so I_m not clear on why I get this behavior, but it makes it difficult to work with the Sun version. Do you have any thoughts on how to correct this?
  
  Either use the Del key instead of the Back-Space, or change your terminal line settings by running the command: stty erase ^H where ^H is typed in by keying Control-V and then Back-Space.
  
  
• (With) regards to entering many commands. While you told us about the method to load files in Smalltalk: 'emp1.st' r This seems to work fine. After I did this, I was able to type the following: emp <- Employee new However, if I entered this same command in a file (like 'test.st'), then entered the command to load the file: 'test.st' r I got an unrecognized command error. What_s wrong with what I did ? I thought the file read command did nothing but enter the lines on the command line a though they were typed.
  
  A file which is loaded in (like: 'emp1.st' r) may contain class and method definitions, but not commands or message sends (like: emp <- Employee new). Those must be entered in the Smalltalk command line. However, you can use I/O redirection at operating system level. That is, you can create a file named, e.g., test.in, with the two lines:
  'emp1.st' r
  emp <- Employee new
  and then run from the Unix or DOS command line: st < test.in.
  
  
• Is there a quick and easy way to capture all of the I/O of a program to a file ? I ended up executing Smalltalk and using the 'tee' command: st |& tee results The output of the program was captured in results, but the input was not. Do you have a standard way of doing this ?
  
  Take a look at script.st.
  
  
• When I goto the directory /course/com3230/bin and execute the file smalltalk.st...i get a ">" prompt. How do i get out of the prompt?
  
  EOF (^D in Unix, ^Z in MSDOS)
  
  
• What is the 'dedicated mailing list' to which you referred in class?
  
  Actually there is none. But there are two useful aliases. com3230-grader@ccs is the address to which you ought to send problem sets for evaluation; and com3230@ccs is the address to which I use to broadcast notes to all of you.
  
  
• Is there going to be a make-up period scheduled for last Thursday_s class? (which was cancelled due to bad weather)
  
  There will definitely be one, but I yet to find out exactly when. Probably in the 11th week.
  
  
• I noticed that Problem Set 2 has been posted. Are both Problem Sets 1 and 2 due in class on Thursday?
  
  No. 1 is, 2 is due a week later. The precise due date appear on the assignment.
  
  
• The system gives me an "Out of Object Allocation" error message. Do you know if there is any way to get around it?
  
  There is no easy way. But take it as an indication that your program must be far from optimal.
  
  
• I still do not quite understand what Overloading is.
  
  Method overloading: two distinct methods which "by coincidence" have the same name m. Two methods are named m "by coincidence" if they are not redefinitions of the same super-method m. Otherwise, they "override" rather than "overload" the super-method, and this would also explain why they are both named m.