In CS70, you will often be working with code supplied by the professor as part of the assignments. Only code provided by the professor, or written by yourself, may be used to complete assignments. Even if you think a particular bit of code is not central to the essence of the assignment, you may not use code written by anyone other than the professor or yourself.
If you have any questions about this policy, ASK FIRST. In the past, students have gotten into serious trouble because they assumed something was OK without asking first.
More information on the honor code can be found on the administrivia page.
The program for this assignment, and everything else except the README file, is due at 10 PM on Wednesday, September 11th, 2002. The README file is due at 1 AM on the following day (Thursday). Refer to the homework policies page for general homework guidelines.
This assignment has several purposes:
You have been hired by a small company that develops Web sites. Your first job will be to make modifications to a system developed by the firm's star programmer, who was recently killed in a tragic unicycling accident.
The system that the programmer developed is large and complex, but the programmer did a good job of dividing it up into small pieces. He even wrote special test programs that exercise the fundamental classes that the system uses. You have determined that you will need to modify one of those classes, which performs arithmetic on rational numbers.
Unfortunately, when you look at the code for the class and its test program you are dismayed, for it seems that the star programmer was far more concerned with whether the code worked than whether it was maintainable. In fact, it seems that he religiously followed the unmaintainability rules. After a few minutes, you go to your boss and tell her that it will be quicker to first spend time cleaning up the programming style, and only make the necessary modifications after the program has been made readable. Your boss agrees, and because the original code is so bad, she will even allow you to do a bit of renaming that will have effects elsewhere (see Tricky Stuff).
Your task for homework #1 is to clean up the style of the rational-number class and its associated test program. There are no known bugs in the program, so you can concentrate on simply cleaning it up without changing the output produced by the test program.
The program is composed of three files:
In addition, there is a so-called Makefile,
which makes it easy to compile the program on Turing by simply typing
make at the command prompt.
WARNING: the Makefile is very
sensitive to how you download it. Do not simply select the text in
your browser and the paste it into an editor window, or
make will not work. Instead, follow the instructions
below. If you download the file individually, you must name it
"Makefile" or "makefile", using exactly that capitalization, or again
make will not work.
The best way to acquire all of these files is to download all of them as a
group. We have provided a tar archive
for Unix/Linux users
and a zip archive for use with DOS and
Windows.
First, create a new directory to hold your
homework, and change into it.
Right-click on the appropriate link in
your Web browser and select "Save link as...". Save the tar or zip
archive in your cs70/hw01 directory.
After the file is saved, you can unpack it into that directory
by typing "gzcat hw01files.tgz | tar xvf -" under
Unix/Linux, or by running "unzip hw01files.zip" under DOS/Windows.
Alternatively, you could right-click on the link for each individual file and choose "Save link as..." to download it separately.
Your final submission should consist of five files:
Makefile
Your Makefile must work correctly, and
must produce an executable named
assign_01. The graders will be using
make to compile your program. If you have
trouble getting make to work, first check to
be sure that you downloaded the
Makefile correctly. If that doesn't cure the problem, ask
one of the graders or professors for help.
assign_01.cc
rat.hh
rat.hh. You are allowed to
choose any name you like, so long as:
.h or
.hh suffix, and
rat.cc
rat.cc. You are allowed to
choose any name you like, so long as:
.cc suffix (or
another
extension accepted by g++,
make still works
with the name and suffix you choose.
README
You should create all of these files in a single directory that is
dedicated to this assignment. You can create a directory using the
h
When you are ready to submit your program,
If you discover a mistake in your program, you can resubmit it using
the same command. You can submit as many times as you like; only the
last version will be used.
Since the README file is due later than the rest of the assignment,
you must submit it separately (unless you have it done before the
deadline). You can do this with the
mkdir command. I suggest that you have a "cs70"
directory that will hold all assignments, and then a subdirectory for
each individual assignment. For example, you might type the following
commands:
mkdir cs70
cd cs70
mkdir hw01
cd hw01
gzcat hw01files.tgz | tar xvf -
emacs assign_01.cc
cd into the
proper directory (e.g., cs70/hw01) and run the
cs70submitall command. This command will prompt you for
the assignment number (see the top of this Web page),
and will then capture all of the source files,
Makefiles, and README files in your directory, so BE
CERTAIN that you don't have anything in your directory
besides your assignment. Remember to
submit early and
often.
cs70submit command:
cs70submit README
If you already submitted your code separately, DO NOT use
cs70submitall to submit the README file, or it will
appear that you missed the deadline even
though you were really on time.
The class defined by rat.hh and rat.cc
implements a simple rational-number package. Rational numbers are
represented as a pair of integers, the numerator and denominator. For
convenience, the class ignores the fact that any real-life computer
imposes a maximum value on integers.
The code you have been given is, to the best of our knowledge, correct and bug-free. However, it is written with very bad style. Your sole task is to improve the style, not to fix bugs. If you find any bugs, you should note them in the README file but should not fix them. (If you find no bugs, the README should mention that there are no known bugs.)
The requirement of no bug fixing is, perhaps surprisingly, very realistic. As a general rule, when you are correcting style in the real world, you should not fix bugs at the same time. If you follow this rule, it will be much easier to find out what happened after the fact, especially when you use a source-code control system (a subject you will study later, in CS121).
The revised class and test program must produce output identical to
that from the
original. You can check that the output is correct using the
diff command. Before you start editing the program, do a
test run and save the output, as follows (% represents your
shell prompt, which will almost certainly be different on Turing):
% make
% ./assign_01 > original.out
The above commands will compile the program (make), run
it (./assign_01), and save the output into a file named
original.out (> original.out). You can
use that file later to make sure the output
hasn't changed.
There are a lot of things wrong with the program in this assignment. Here are some hints about what you might want to play with:
As mentioned above, you can compile the program by
simply typing make at the command prompt. One of the
many advantages of using make is that it will run the
compiler with switches that check for all sorts of simple errors.
Your program must compile without any warning messages when
the compiler is invoked with the -Wall -pedantic switches
(as happens when you use make).
If you are new to Unix, you may be wondering how you can test your program.
To run your program, simply type "./assign_01" (without
the quotes). Since this program requires no input, you should
immediately see the output on your terminal. If the program
misbehaves badly, you can abort it by typing control-C.
You can look at the output of the original version by typing cat
original.out. Alternatively, you can use the
diff command to compare the output of the original with
the output of the new version:
% ./assign_01 | diff original.out -
If the two versions produce identical results, you will see no output
on your screen. For example, if you changed "yup" to "yessss!", you
would see something like:
9c9
< yup
---
> yessss!
Every assignment in CS70 must be
accompanied by a README file. The file
must be named README in all uppercase
letters. A detailed specification of the README file can
be found on the homework
policies page. For this assignment, make sure the
README file contains:
For the most part, you should be able to complete this assignment without knowing anything special about C++. However, it will help to know a few things:
RationalNumber that is implemented in a
pair of files
named rational.cc and rational.hh.
class declaration. However, for this
assignment you are allowed to leave the code where it is.
Just make it pretty.
const keyword and the
& symbol. Just trust that they are correct.
a = b;).
a += b;).
++a or
a++). There
are two versions of this operator, one with
and one without an int argument.
The first version implements ++a
and the second handles a++.
a + b).
a - b).
a * b).
a / b).
a < b).
a == b).
There are now two versions of the GNU C++ compiler (g++) on Turing:
g++ and g++3. The latter is newer, slower,
and less stable. However, it also produces better error messages, so
it is worth learning to use it.
To use g++3, edit your Makefile and change
the line that says:
CXX = g++so that it reads:
CXX = g++3Then type "
make clean" and "make" to
recompile your program.
With every assignment, there are parts that can surprise you. Some of the "gotchas" in this assignment include:
make will not work.
make
clean" followed by "make". That will
usually reveal any problems that might have been masked by an
incorrect Makefile. (This will become important on later
assignments.)
/* * I'm not yet sure what the next three lines do. I think they have * something to do with handling end-of-file. GHK 1/19/00 */
There is more information on using C++ on Turing available in the departmental quick-reference guide and the C++ quick reference guide.
© 2002, Geoff Kuenning
This page is maintained by Geoff Kuenning.