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Software Development Methods Assignment 2

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Software Engineering 265
Software Development Methods
Assignment 2

Programming environment
For this assignment you must ensure your work executes correctly on the Linux
machines in ELW B215 (i.e., these have Python 3.4 installed). You are free to do
some of your programming on your own computers; if you do this, give yourself a
few days before the due date to iron out any bugs in the Python script you have
pushed to your remote repository.
Individual work
This assignment is to be completed by each individual student (i.e., no group work).
Naturally you will want to discuss aspects of the problem with fellow students, and
such discussion is encouraged. However, sharing of code fragments is strictly
forbidden without the express written permission of the course instructor
(Zastre). If you are still unsure regarding what is permitted or have other questions
about what constitutes appropriate collaboration, please contact me as soon as
possible. (Code-similarity analysis tools may be used to examine submitted
programs.)
Objectives of this assignment
• Learn to use basic features of the Python 3 language. This is available as
python3 from the command line, or /opt/bin/python3 on the ELW B215
machines. Alternatively you can use #!/usr/bin/env python3 in your bang
path.
• Use the Python programming language to write a less resource-restricted
implementation of “format265” (but without using regular expressions).
• Use Git to manage changes in your source code and annotate the evolution of
your solution with “messages” provided during commits.
• Test your code against the twenty provided test cases.
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This assignment: “format265.py”
You are to write a Python version of the program you prepared for assignment #1.
All of the formatting capabilities of that C program are to be implemented in this
new program. Like the C program, it must run as a command in the shell. (Beware,
though: You do not want to attempt porting you C solution into Python!) There are
several additional abilities your Python script must have:
• If a filename is provided to the script, then that file’s contents are
formatted. If no filename is provided, then the contents of stdin are
formatted. In either case, the formatted output is sent to stdout.
• The “.LW”, “.LM” and “.FT” commands may appear at any line of the input file.
As in assignment #1, such commands are valid only if they appear at the start
of a line.
• The margin may now be specified relative to the value of the current margin
position. For example, if the margin currently is 10, then when “.LM +5” is
encountered the margin would be set to 15. If the margin currently is 20,
then “.LM -7” would set the margin to 13, and a further “.LM -7” would set the
margin to 6.
• Valid margins must be (a) greater than or equal to 0, and (b) less than or
equal to the page width minus 20. If a margin would be negative after a “.LM”
command, then the margin is set to zero. If a margin would be greater than
then page width minus 20, then the margin is set to page width minus 20.
• For this assignment, a “.LM” will never be immediately followed (i.e., on the
next line) by another “.LM” command.
• The linespacing command (.LS) will never have values greater than 2.
• There is no limit to the number of input lines. You may assume that each
input line is no longer than 132 characters.
With your completed “format265.py” script, the input would be transformed into
the output (here redirected to a file) and then checked:
% ./format265.py /home/zastre/seng265/assign2/tests/in11.txt > ./myout11.txt
% diff /home/zastre/seng265/assign2/tests/out11.txt ./myout11.txt
where the file “myout11.txt” would be found in your current directory.
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Exercises for this assignment
1. Within your Git project create an “assign2” local repository. Use the test files
in /home/zastre/seng265/assign2/tests. (Files in01.txt through to
in10.txt are the same as those used for the first assignment.) Your
format265.py script must appear in this assign2. Ensure the subdirectory
and script file are tracked by Git.
2. Write your program. Amongst other tasks you will need to:
• read text input from a file, line by line
• read text input from stdin, line by line
• write output to the terminal
• extract substrings from lines produced when reading a file
• create and use lists in a non-trivial array
• use the “diff” Unix command to test the output of your program
3. Keep all of your code in one file for this assignment. We will explore Python’s
object-oriented features and module-authoring mechanism in the next
assignment (i.e., Assignment #3).
4. Use the test files to guide your implementation effort. Start with simple cases
(such as those given in this writeup). Refrain from writing the program all at
once and budget time to anticipate when “things go wrong”.
5. For this assignment you can assume all test inputs will be well-formed (i.e.,
our teaching assistant will not test your submission for handling of input or
for arguments containing errors). Later assignments will specify errorhandling as part of the assignment.
6. Reasonable run-time performance of your script is expected. None of the test
cases should take longer than 15 seconds to complete on a machine in ELW
B215.
What you must submit
• A single Python script file named format265.py containing a solution to
Assignment #2 within your Git repository in a directory named assign2.
Evaluation
Students may be selected to demonstrate their work to a member of the course’s
teaching team. Student demo lists will be posted onto conneX several hours the due
date. Those selected for a demo must sign up for a demo slot; each demo will require
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about 10 minutes. Details of the sign-up process will be posted on conneX as an
announcement.j
Our grading scheme is relatively simple.
• “A” grade: An exceptional submission demonstrating creativity and initiative.
“format265” runs without any problems. The program is clearly written and
uses functions appropriately (i.e., is well structured). Evaluation of your extra
work would be easier if you could include a second version of your
assignment with the extra features (naming the file format265_extra.py).
• “B” grade: A submission completing the requirements of the assignment.
“format265” runs without any problems. The program is clearly written.
• “C” grade: A submission completing most of the requirements of the
assignment. “format265” runs with some problems.
• “D” grade: A serious attempt at completing requirements for the assignment.
“format265” runs with quite a few problems.
• “F” grade: Either no submission given, or submission represents very little
work.

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