题意：
实现一个根据指令生成特定格式字符的系统
解析：
stage1：
读取文本中的输入，忽略以"."开头的字符串，以单空格替换文中可能出现的多个空格，并且当输出行字符超过50个字符能够自动换行，在输出行与左边框的距离默认有4个空格。
stage2：
扩展stage1的程序，使其能够接受以下的命令
.b 忽略之后当前行之后的字符，跳到下一行开始输出
.p 打印一个空行，开启一个新的段落
.l nn 将与左边框的距离更改为nn
.w nn 将每行的最大宽度更改为nn
stage3：
在stage2的基础上增加指令
.c 居中指令，将之后的内容置于当前行的中间
.h nn 标题指令，按照nn将后面的内容制作为标题，最高有五级标题
涉及知识点：
字符处理，文件读写
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School of Computing and Information Systems
comp10002 Foundations of Algorithms
Semester 2, 2019
Assignment 1
Learning Outcomes
In this project you will demonstrate your understanding of arrays, strings, and functions. You may
also use typedefs and structs if you wish (see Chapter 8) – and will probably find the program
easier to assemble if you do – but you are not required to use them in order to obtain full marks. You
should not make any use of malloc() (Chapter 10) or file operations (Chapter 11) in this project.
Text Formatting
We all want our written work to look good. But when preparing text with a text editor it is annoying
to (for example) try and adjust the line-lengths in a document every time we alter it, or if we decide
that the text width needs to be narrower. So we use approaches that let us describe the layout of
documents, and apply a compiler-like tool to generate the exact formatting that we are after. For
example, this document (and most other things you will see in this subject, including the textbook)
was prepared using a typesetting tool called LATEX, and you can see the source code for it linked from
the LMS/FAQ page. Use of LATEX allows math expressions like →∞∑
more complex expressions too) to be elegantly presented, and allows careful and consistent formatting
to be applied throughout long documents. A WYSIWYG1(or more usually, WYCSIAYCG2) tool like
Word might be employed to write a one-page reference letter, but for technical work academics in the
maths, physics, and computing sciences almost always prefer LATEX. (It was originally invented by one
of the most famous computer scientists of all, Stanford University’s Donald E. Knuth, and now has
a world-wide community of developers and language extenders.) Similarly, html tags in conjunction
with a style sheet file describe how the contents of a web page are to be rendered and presented.
In this assignment we are going to journey back to the 1970s, and implement a simple text formatting tool based entirely on fixed-width terminal fonts and character-based output.3 The formatting
“commands” will be indicated by input lines that start with a period, “.”, with the command indicated
by the letter in the next character position. For example, the characters “.p” in the first two positions
of a line are (in this simple language) the signal to start a new paragraph in the output.
Stage 1 – Filling Lines (8/15 marks)
The first version of your program should:
• read text input from stdin (you may assume that input lines will be at most 999 characters long);
• completely discard the content of all lines that commence with a period character;
• replace all instances of (multiple) whitespace characters (blanks, tabs, newlines) by single blanks;
• re-insert newline characters in a greedy line-by-line manner, so that each output line emitted is as
long as possible, but not longer than 50 characters;
• with the exception that if there is an input token/word that is greater than 50 characters, it goes on
an output line by itself, and that line can be greater than 50 characters long.
1What you see is what you get.
2What you can see is all you can get.
3Alistair wrote his 1985 PhD thesis using a tool like this, see http://hdl.handle.net/10092/7926; Artem is
younger, he used LATEX for his thesis in 2012, see https://publishup.uni-potsdam.de/frontdoor/index/index/
docId/5705.
The lines in the output should be arranged so that the left margin has a default of 4 initial blanks, and
hence that the first non-blank character in each line is in column 4 (counting the columns from zero),
and the last character in any line (except as noted in connection with very long tokens) is never beyond
column 53 in each output line. For example, if the file test0.txt contains
one two three four five six seven eight
nine
ten eleven twelve thirteen fourteen
fifteen sixteen
seventeen
eighteen nineteen twenty.
.b
Enough of the numbers already, what about:
101, 102, 103, 104, 105, 106, 107, 108, and 109?
Plus 110, 111, 112, 113, 114 and all of 115 116 117 118 and 119.
the output should be
0----5—10—15—20—25—30—35—40—45—50—55—60
mac: ass1-soln < test0.txt
one two three four five six seven eight nine ten
eleven twelve thirteen fourteen fifteen sixteen
seventeen eighteen nineteen twenty. Enough of the
numbers already, what about: 101, 102, 103, 104,
105, 106, 107, 108, and 109? Plus 110, 111, 112,
113, 114 and all of 115 116 117 118 and 119.
mac:
0----5—10—15—20—25—30—35—40—45—50—55—60
where the two “rulers” are not part of the output and are provided here to help you count character
positions. (But, hint hint, they were part of the output while the sample solution was being debugged.)
See the FAQ page linked from the LMS for more example input files and the output that is expected.
Note that the values 4 and 50 should be held in variables assigned via initial #define starting points
– you will need to be able to change their values in Stage 2.
The getword() function that was discussed in class may look like a tempting starting point. But
you need to be able to examine the first character of each line without necessarily consuming it, and
so a main loop that reads and processes lines is probably a better bet. You can then break that line up
into tokens as required. You should also pay close attention to the item on the FAQ page that discusses
the issues that may arise in connection with newline characters.
Note also that while it is possible to achieve the limited functionality required in this stage with a
program that is little more than a “while (getchar())” loop, you will only receive 8/8 for a Stage 1
submission if your program shows that you have planned it in a way that allows the functionality
required for Stage 2 and Stage 3 to be added without needing to completely rewrite it.
Stage 2 – Processing Commands (13/15 marks)
Once you have the Stage 1 program operational (and submitted, so that it is “on the record”), extend
your program so that it recognizes and acts upon the following commands, where the “.” that indicates
a formatting command always appears in the first position of an input line, straight after a newline
character:
• .b – break the current line, so that the next input token starts at the beginning of the next line;
• .p – leave a blank line and start a new paragraph without altering the margins, with the next input
token starting the new paragraph;
• .l nn – alter the left margin from its current value (default initial value of 4) to the new value nn,
and start a new paragraph;
• .w nn – alter the width of each line from its current value (default initial value of 50) to the new
value nn, and start a new paragraph.
There are further examples showing the required output linked from the LMS.
Stage 3 – Adding Structure (15/15 marks)
Now add two further commands:
• .c – take the remaining contents of this line and center them within the current output width. If
the remaining contents cannot fit within the current output width, then it should be placed so that
it starts at the left margin and overflows beyond the current width. When there is an odd number
of spaces to be assigned, the rounded-down half should be at the beginning of the line, and the
rounded-up half at the end of the line.
• .h nn – take the remainder of the contents of this line and use them as a section heading at the
level indicated by nn. The Section/subsection/subsubsection number should be printed, and then
the complete heading on a single line, even if it is longer that the current width. Headings at level
nn reset the numbering for headings level nn + 1, nn + 2, and so on; and (to avoid non-computing
people from being confused) all headings start their counting from one. At most five levels of
headings may occur, counting from nn = 1 (the top-level heading) to nn = 5. All headings are
always preceded and followed by a paragraph boundary, and level-1 headings are also preceded
by a full-width line of “-” characters.
Again, see the FAQ page for linked examples of input and output combinations.
Beyond the Scope of the Project
Bored? Fidgetty? Lost interest in facebook? How about:
• .i – make an item in a bulleted list, just like this sentence is part of a bulleted list generated by
LATEX. Use a “o” as the “bullet” character, and indent the left margin by three characters and
reduce the width by three spaces, until then next “.p” or “.b” command occurs, which ends the
bulleted list. (But please dont submit any such programs for assessment, even if you get them
working prior to the submission deadline.)
• Or, if you want to do something even more rewarding, find an on-line LATEX tutorial, install one of
the many free LATEX packages, and teach yourself how to make professional-looking documents.
(And you’ll never have to fight with Word again. . . )
General tips…
You will probably find it helpful to include a DEBUG mode in your program that prints out intermediate data and variable values. Use #if (DEBUG) and #endif around such blocks of code, and then
#define DEBUG 1 or #define DEBUG 0 at the top. Turn off the debug mode when making your
final submission, but leave the debug code in place. The FAQ page has more information about this.
The sequence of stages described in this handout is deliberate – it represents a sensible path though
to the final program. You can, of course, ignore the advice and try and write final program in a single
effort, without developing it incrementally and testing it in phases. You might even get away with it,
this time and at this somewhat limited scale, and develop a program that works. But in general, one of
the key things that makes some people better at programming than others is the ability to see a design
path through simple programs, to more comprehensive programs, to final programs, that keeps the
complexity under control at all times. That is one of the skills this is subject is intended to teach you.
And if you submit each of the stages as you complete it, you’ll know that you are accumulating evidence should you need to demonstrate your progress in the event of a special consideration application
becoming necessary.
The boring stuff…
This project is worth 15% of your final mark. A rubric explaining the marking expectations is provided
on the FAQ page. You need to submit your program for assessment; detailed instructions on how to
do that will be posted on the FAQ page once submissions are opened. Submission will not be done via
the LMS; instead you will need to log in to a Unix server and submit your files to a software system
known as submit. You can (and should) use submit both early and often – to get used to the way
it works, and also to check that your program compiles correctly on our test system, which has some
different characteristics to the lab machines. Failure to follow this simple advice is highly likely to
result in tears. Only the last submission that you make before the deadline will be marked. Marks and
a sample solution will be available on the LMS before Tuesday 8 October.
Academic Honesty: You may discuss your work during your workshop, and with others in the class,
but what gets typed into your program must be individual work, not copied from anyone else. So, do
not give hard copy or soft copy of your work to anyone else; do not “lend” your “Uni backup” memory
stick to others for any reason at all; and do not ask others to give you their programs “just so that I
can take a look and get some ideas, I won’t copy, honest”. The best way to help your friends in this
regard is to say a very firm “no” when they ask for a copy of, or to see, your program, pointing out that
your “no”, and their acceptance of that decision, is the only thing that will preserve your friendship.
A sophisticated program that undertakes deep structural analysis of C code identifying regions of
similarity will be run over all submissions in “compare every pair” mode. Students whose programs
are so identified will either lose marks through the marking rubric, or will be referred to the Student
Center for possible disciplinary action without further warning. This message is the warning. See
https://academicintegrity.unimelb.edu.au for more information. Note also that solicitation
of solutions via posts to online forums or marketplaces, whether or not there is payment involved,
is also Academic Misconduct. In the past students have had their enrollment terminated for such
behavior.
The FAQ page contains wording for an Authorship Declaration that you must include as a
comment at the top of your submitted program. A significant fraction of the available marks
will be deducted if you do not do so.
Deadline: Programs not submitted by 10:00am on Monday 23 September will incur penalty marks
at the rate of two marks per day or part day late. Students seeking extensions for medical or other
“outside my control” reasons should email [email protected] as soon as possible after
those circumstances arise. If you attend a GP or other health care service as a result of illness, be
sure to take a Health Professional Report (HPR) form with you (get it from the Special Consideration
section of the Student Portal), you will need this form to be filled out if your illness develops in to
something that later requires a Special Consideration application to be lodged. You should scan the
HPR form and send it with any non-Special Consideration assignment extension requests.
And remember, algorithms are fun!
