UMBC CMSC 201, Computer Science I, Fall 1995
Sections 0101, 0102, 0103 and Honors
Project 3 Comments
People have been asking pretty much the same questions.
So, let's just summarize the answers.
- The normal form for zero is 0/1.
- Make sure that your LessThanFraction function
works when you compare 7/8 versus 3/4 and 5/8 versus 3/4.
If you have a whole bunch of if statements for this function,
chances are that you don't have it right.
- If you want to submit a new version of your project, just
resubmit it. We will grade the most recent submission.
- If you want to have extra functions (e.g., the GCD
function), you should put the prototypes for these functions at
the top of your proj3.c file. Since these
functions are not used by functions in other files,
they do not belong in proj3.h.
- The return value of the functions AddFraction, etc. should
be in normal form. That is the numerator and the denominator
should not have any common divisors greater than 1, and the
denominator should not be negative.
- If you are having trouble with MakeFraction returning values
that are not in normal form, check your ReduceFraction
function. Several people complained about having a negative
denominator, but it turns out that they tried to take the
GCD of a positive and a negative number. The GCD algorithm
from the book is for positive numbers only.
- Think about what you want to do if someone calls your
functions with unreduced fractions (e.g., 2/4). You basically
have 3 options.
Think about these cases. Which one do you want to implement?
All three are "allowed" because it is not part of the "contract"
that your functions should handle fractions not in normal form.
Clearly, the last option is nastiest. The first option is
not bad, perhaps a bit unfriendly. The second option is
"nice" but this means your functions have some undocumented features.
This could lead to incompatibility problems in the future.
Finally, what does your EqualFraction function do?
Your function could crash. That is, your function checks to see if
the fractions are reduced. If they are not then you use the Error
function to halt the entire program and return control to the
Your function could guarantee that the correct answer is
produced, even if the function is called with unreduced
Your function could be unpredictable and sometimes quietly
produce the wrong answer.
By the way, if you send me email to ask me a specific question, do not send
the email anonymously. I won't be able to reply to you. You should
also include your program (use read in PINE, no MIME attachments please)
so I can see what you are doing. I will try to do my best, but it is
very difficult to guess who you are and what your problem is if you
don't tell me anything!
Thu Oct 26 14:29:34 EDT 1995
Richard Chang, email@example.com