FIT2014

DUE: 11:55pm, Friday 19 August 2022

Introduction to awk
In an awk program, each line has the form
/pattern / { action }
where the pattern is a regular expression (or certain other special patterns) and the action is an
instruction that specifies what to do with any line that contains a match for the pattern. The action
(and the {...} around it) can be omitted, in which case any line that matches the pattern is printed.
Once you have written your program, it does not need to be compiled. It can be executed di-
rectly, by using the awk command in Linux:
$ awk -f programName inputFileName
Your program is then executed on an input file in the following way.
// Initially, we’re at the start of the input file, and haven’t read any of it yet.
If the program has a line with the special pattern BEGIN, then
do the action specified for this pattern.
Main loop, going through the input file:
{
inputLine := next line of input file
Go to the start of the program.
Inner loop, going through the program:
{
programLine := next line of program (but ignore any BEGIN and END lines)
if inputLine contains a string that matches the pattern in programLine, then
if there is an action specified in the programLine, then
{
do this action
}
else
just print inputLine // it goes to standard output
}
}
If the program has a line with the special pattern END, then
do the action specified for this pattern.
Any output is sent to standard output.
You should read about the basics of awk, including the way it represents regular expressions and
the main instruction types used in its actions. Any of the following sources should be a reasonable
place to start:
• A. V. Aho, B. W. Kernighan and P. J. Weinberger, The AWK Programming Language,
Addison-Wesley, New York, 1988.
(The first few sections of Chapter 1 should have most of what you need, but be aware also of
the regular expression specification on p28.)
2
• https://www.grymoire.com/Unix/Awk.html
• the Wikipedia article looks ok
• the awk manpage
• the GNU Awk User’s Guide.
Introduction to Problem 1
The Master said, ‘What is necessary is to rectify names .... If names are not recti-
fied, then words are not appropriate. If words are not appropriate, then deeds are not
accomplished.’
– Confucius (孔夫子), The Analects (transl. R. Dawson), Oxford University Press,
1993, §13.3.
Most organisations today deal with people from many different cultures and language groups,
and they must often record and process people’s names in systems that work mainly with English
language text. In such contexts, it is helpful to be able to recognise names from different language
groups. Example applications include: determining how to pronounce students’ names when reading
them out from a list at graduation ceremonies; determining how to greet a person with whom you
have an appointment; determining how to enter the various parts of a person’s name into a database;
determining how automatically-generated emails, sent to many different people listed in some file,
should address each recipient; determining the most likely native language of a person in situations
where their name is known but they cannot be spoken to directly at the time (e.g., in some emergency
situations). Recognising the language group that a name belongs to is an important first step in all
these situations.
In this problem you will write some code in sed and awk to try to recognise one type of names in
a long file of Asian names. More specifically, suppose you are given an input file in which each line
starts with a person’s name in some language, with each name transcribed somehow into English
text. Your task is to detect which of these names come from Korean.
In the input file, all text from the start of each line until the first colon (:) on the line (but not
including the colon itself) is taken to be a person’s name. In most cases, each line ends with a string
of non-blank letters specifying which language the name is believed to come from. An example input
file is provided, as inputFileOfNames. If you browse through the file, you will notice that it contains
names from a variety of Asian languages: Mandarin, Cantonese, Hokkien, Teochew, Hakka, Korean,
Japanese, Thai, Vietnamese, Malay and Indonesian. They have been represented in English text
using a variety of transcription schemes, and with all extra marks on letters (accents, tone marks,
other diacritical marks, etc.) removed.
In many cases, the line about a person also contains some
other information about them, but our name recognition task will ignore that information. 3
Further information about working with names from different cultures can be found in:
• Fiona Swee-Lin Price, Success with Asian Names, Allen & Unwin, Crows Nest, NSW, 2007.
• J. Greenberg Motamedi, Z. Jaffery, A. Hagen, and S. Y. Yoon, Getting it right: Reference guides
for registering students with non-English names, 2nd edition. (REL 2016-158 v2), U.S. Depart-
ment of Education, Institute of Education Sciences, National Center for Education Evaluation
and Regional Assistance, Regional Educational Laboratory Northwest, Washington, DC, 2017.
https://ies.ed.gov/ncee/edlabs/regions/northwest/pdf/REL_2016158.pdf
• SBS, The Cultural Atlas, https://culturalatlas.sbs.com.au/. You can look up a country
or culture (e.g., by clicking on a map) and then click on a link to “Naming” for that culture.
1 There are a few romanisation systems for transcribing Korean into English.
2 These marks carry important information about meaning and pronunciation. But they are often removed when
names are represented using other alphabets.
3 The
file was compiled from a number of sources, mainly Wikipedia lists of names of type
https://en.wikipedia.org/wiki/List of CultureName people, where CultureName is one of the cultures listed
above; also https://www.goratings.org/en/. The lists obtained from Wikipedia are rather imperfect, with peo-
ple’s names often not written in a form that clearly shows the claimed cultural background.
Names in Korean
Korean names consist of a family name followed by a given name (the reverse of the usual order
in English). The family name usually consists of just a single syllable, and the given name usually
consists of two syllables. We restrict ourselves to names with these numbers of syllables from now
on. 4
We treat a Korean name as consisting of a syllable, followed by a space, followed by two consec-
utive syllables which may have a hyphen between them.
Each syllable consists of an optional prefix, a compulsory middle and an optional suffix. 5
• The possibilities for the prefix are:
g, kk, n, d, tt, r, m, b, pp, s, ss, j, jj, ch, tch, k, t, p, h
These are also listed, one per line, in the file prefix-file.
• The possibilities for the middle are:
a, ae, ya, yae, eo, e, yeo, ye, o, wa, wae, oe, yo, u, wo, we, wi, yu, eu, ui, i, oo, ah
These are also listed, one per line, in the file middle-file.
• The possibilities for the suffix are:
k, n, t, l, m, p, ng
These are also listed, one per line, in the file suffix-file.
For example, the syllable kyung is formed from the prefix k followed by the middle yu and then the
suffix ng.
Constructing a regular expression for Korean names
We will use this information, together with sed, to generate a regular expression to try to match
Korean names. (The match will be quite imperfect, and later you will do some simple computations
to get some idea of how well, or poorly, it does. 6 ) Throughout, we will only do case-insensitive
matching, so there is no need to capitalise initial letters of syllables in order to match names.
We describe the steps in detail now, and then list the assignment submission requirements for
Problem 1.
We start with the file Korean-NameStructure0, which just contains one line consisting of the
text <NAME>. Think of this as a special symbol, eventually to be transformed to a regular expression
for Korean names.
We first transform <NAME> to a regular expression representing the syllable structure of Korean
names. From our description of the syllable structure above, we can represent this by the regular
expression <SYLLABLE> <SYLLABLE>-?<SYLLABLE> where <SYLLABLE> is a special symbol to repre-
sent any Korean syllable and putting “?” after a symbol means it can occur just once or not at
all at that position. 7 Each occurrence of <SYLLABLE> will eventually be transformed to a regular
expression to represent such syllables. The first step of this transformation can be done using the
4 There are exceptions, though they are uncommon: some family names have two syllables, and some given names
have one syllable or more than two syllables. But in this assignment we consider only one-syllable family names and
two-syllable given names.
5 This terminology is different to the more usual linguistic terminology of initials and finals. This is deliberate,
since they represent slightly different sets of strings here to the standard initials and finals. This change was just a
small simplification for the purposes of the assignment.
6 Some reasons for the imperfect matching include: not all the combinations of prefixes and suffixes listed above
give valid syllables in Korean; some people write Korean names without any hyphen or with a space between the two
syllables of the given name; Korean names are sometimes represented using other schemes; and some family or given
names may have different numbers of syllables than those we have allowed for.
7 The operator “?” is a standard feature of regular expression syntax in sed and awk. Question to consider (but not
part of the assignment): does using it enlarge the class of languages that can be represented by regular expressions?
following sed command:
$ sed "s/<NAME>/<SYLLABLE> <SYLLABLE>-?<SYLLABLE>/" Korean-NameStructure0 > Korean-NameStructure1
Alternatively, you can execute the sed instruction “s/<NAME>/<SYLLABLE> <SYLLABLE>-?<SYLLABLE>/”
from the the file decomposeNameIntoSyllables (provided with this assignment) by doing the fol-
lowing:
$ sed -f decomposeNameIntoSyllables Korean-NameStructure0
> Korean-NameStructure1
Try these, using the given files, and check that you get the required result in the file
Korean-NameStructure1. This use of sed is a template for what you will do next.
Now you need to replace each <SYLLABLE> by a regular expression representing possible syllable
structures, using <PREFIX>, <MIDDLE> and <SUFFIX>.
Write the sed instruction to do this, in the file decomposeSyllablesIntoParts, and do the
transformation from your Linux command line using
$ sed -f decomposeSyllablesIntoParts Korean-NameStructure1
> Korean-NameStructure2
Now you need to replace each occurrence of each part, <PREFIX>, <MIDDLE> and <SUFFIX>, by
regular expressions representing possible letter strings, according to the sets of strings given on the
previous page.
Write the sed instructions to do this, in the file decomposePartsIntoLetters. You will need
three lines: one line giving the sed instruction for each part type, <PREFIX>, <MIDDLE> and <SUFFIX>.
Then do the transformation from your Linux command line using
$ sed -f decomposePartsIntoLetters Korean-NameStructure2
> Korean-NameStructure3
This should put, into the file Korean-NameStructure3, a regular expression that is intended to
match Korean names.
Matching names in the input file
We will now use this regular expression to construct an awk program to apply it to names in the
input file, and to do some simple computations to determine how well the regular expression matches
Korean names.
For each name in the input file, checking it against your regular expression gives one of four
possible outcomes:
• Correct Match: a name that belongs to Korean (according to the last word on its line in
inputFileOfNames) is also matched by your regular expression.
• False Positive: a name that does not belong to Korean (according to the last word on its
line in inputFileOfNames), but is matched by your regular expression.
• False Negative: a name that belongs to Korean (according to the last word on its line in
inputFileOfNames), but is not matched by your regular expression.
• Correct Non-match: a name that does not belong to Korean (according to the last word
on its line in inputFileOfNames) and is not matched by your regular expression.
Your awk program should compute the number of names, in the input file, of each of these four
types, and report those numbers at the end.
You can write the awk program manually, cutting-and-pasting the regular expression as needed
(and making any necessary modifications to it) from Korean-NameStructure3.
The heart of your awk program will be a statement that does the following.
• The pattern matches a Korean name whenever it occurs in the specified position at the start
of a line.
– Recall the general structure of an awk statement. By default, matches in awk are case-
sensitive. To do a case-insensitive match, you need to match the pattern against a version
of the current line in which all alphabetic characters have been converted to lower case.
This can be done using a statement of this form:
tolower($0) ~ /pattern / { action }
Here, $0 is a built-in awk variable that always contains the current line of the input file,
and tolower() is a function that converts all alphabetic characters to lower case. You
can read “ ~ ” as “matches”.
• The action increments appropriate variables in order to update the number of correct matches,
false positives, false negatives, or correct non-matches, as appropriate.
You may need another line or few too, including an END line, at the end, in order to print the total
numbers of matches of each type.
The files and commands required to complete this problem are shown in Figure 1.
Problem 1. [12 marks]
First, run sed, as described, using the one-line sed script decomposeNameIntoSyllables to produce
Korean-NameStructure1.
(a) Write the one-line sed script, decomposeSyllablesIntoParts, and run sed, as described, to
produce Korean-NameStructure2.
(b) Write the three-line sed script, decomposePartsIntoLetters, and run sed, as described, to
produce Korean-NameStructure3.
(c) Write the awk script, matchKorean, and run it, as described, on input file inputFileOfNames,
to produce outputFile.
For bonus marks:
NOTE: This is a more advanced and challenging exercise, requiring exploration, experimentation,
and research. To attempt it, you must have mastered the rest of this question first. Bonus marks
are only available when the total mark for the rest of Problem 1 is at least 10 out of 12.
Can you write a much better regular expression for Korean names? If you attempt this, then, in
addition to the files required above, you should also provide:
• your new regular expression, in a one-line file called Korean-NameStructure4;
• your new awk program, in a file called matchKoreanBonus;
• the output from running your awk program on the input file, as outputFileBonus.
To qualify for bonus marks, your approach must use a significantly different approach to the one
used above, and offer a significant advantage. If your approach is more complex, then it should give
better results (i.e., lower error rate) in general. If your approach is significantly simpler but does
almost as well, then that also may qualify for bonus marks.
Korean-NameStructure0
sed -f decomposeNameIntoSyllables Korean-NameStructure0
> Korean-NameStructure1
Korean-NameStructure1
sed -f decomposeSyllablesIntoParts Korean-NameStructure1
> Korean-NameStructure2
Korean-NameStructure2
sed -f decomposePartsIntoLetters Korean-NameStructure2
> Korean-NameStructure3
Korean-NameStructure3
write awk code, using regular expression in Korean-NameStructure3
matchKorean
awk -f matchKorean inputFileOfNames > outputFile
inputFileOfNames
decomposeNameIntoSyllables
decomposeSyllablesIntoParts
decomposePartsIntoLetters
outputFile
Figure 1: The plan.
Your solution will not just be evaluated on how well it does on the provided input file. It will
be run on other files of names too. Also, do not base your regular expression solely on the specific
details of the Korean names provided in the input file. They may not be totally representative of
the full range of names from that culture.
As usual, be sure to cite any sources used.
Problem 2. [8 marks]
An independent set in a graph is a set of mutually non-adjacent vertices in the graph. So, no edge
can have both its endpoints in an independent set.
In this problem, we will count independent sets in ladder graphs. A ladder graph L n is a graph
obtained from the points and lines formed by a row of n squares. More formally:
• its vertices correspond to ordered pairs (0,0),(0,1),(1,0),(1,1),...,(n,0),(n,1);
• two vertices are adjacent if they represent points at distance exactly 1 from each other.
The number n here is called the order of the ladder. Here is L 3 , a ladder of order 3:
(0,1)
(0,0)
(1,1)
(1,0)
(2,1)
(2,0)
(3,1)
(3,0)
Examples of independent sets in L 3 include: ∅, {(2,1)}, {(0,0),(2,0),(3,1)}, {(0,1),(1,0),(2,1),(3,0)}.
The simplest ladder is L 0 , consisting of just the vertices (0,0) and (0,1) with a single edge
between them.
For all n, define
a n = number of independent sets in L n which include neither (n,0) nor (n,1);
b n = number of independent sets in L n which include (n,0) but not (n,1);
c n = total number of independent sets in L n .
(a) Compute a 0 , b 0 , a 1 , b 1 .
(b) Give, with justification, recurrence relations that express a n+1 and b n+1 in terms of a n and b n .
(Here, each of a n+1 and b n+1 is expressed using both a n and b n .)
(c) Prove, by induction on n, that for all n ≥ 0,
a n ≤
√ 2( √ 2 + 1) n
and
b n ≤ ( √ 2 + 1) n .
(d) Hence give a good closed-form upper bound for c n (i.e., an upper-bound expression in terms
of n, not a recurrence relation). Your bound should be significantly better than 3 n (which is the
upper bound you get by ignoring horizontal edges and only taking vertical edges into account).
For bonus marks:
NOTE: This is a more advanced and challenging exercise. To attempt it, you must have mastered
the rest of this question first. Bonus marks are only available when the total mark for the rest of
Problem 2 is at least 7 out of 8.
Find, and prove using similar techniques including induction, good lower bounds for a n , b n
and c n