CSci 3501 Algorithms and Computability - Lab 9.
October 29. Due Wednesday, November 4th at 11:59pm
What to submit and when:
- All submissions are electronic: by e-mail to elenam at morris.umn.edu and CC to all lab
partners. Please do not delete your e-mail from "Sent mail" or your
mailbox until the end of the semester.
- When working on the lab, please comment your work so that it is
clear what contributions of each person are.
- At the end of the lab each group should send me the results of their
in-class work. Please indicate if this is your final submission.
- If your submission at the end of the lab time was not final,
please send me(CC to the lab partner(s)) a final copy before the due
time. Please use the subject "3501 Lab N", where N is the lab
number.
Lab assignment
Work in pairs
Lab overview and goals
The goal of the lab is to practice with JFLAP (a tool for experimenting with
finite automata and other computability topics) and to design and test
finite automata (DFAs and NFAs).
Using JFLAP and naming your files
- Please save your automata files as .jff files and your data as
.txt files. Files names must be as follows: names
of those in the group followed by question name,
e.g.
SmithAdams3.jff
(where 3 refers to the question
number). This will help me in running test data
- To load test data from a file, go to
Input -> Multiple Runs
-> Load Inputs
- When adding multiple transitions between the same two states, add
them one by one. Typing "0, 1" in a label for an arrow will give you
a wrong result since the automaton will try to match this input
exactly, including the comma.
- When writing DFA, check that every state has a transition on every
symbol. JFLAP does not check it.
- Use
Convert -> Combine Automata
to copy one automaton into a file for another one.
- Do not use "convert to DFA" or "minimize DFA" options.
- Consult the JFLAP tutorial as
needed.
Lab tasks
Lab task 1: convert regular expressions to an NFA (8 points)
Use the tutorial Regular
Expressions and Converting to an NFA to convert the regular
expressions given below to NFAs.
Note that JFLAP uses
+ as a symbol for union and * for the star operation. Also make sure
to set parentheses correctly in your expression.
JFLAP gives you hints on the steps
and provides a button "(De)-expressionify Transition" to break down
regular expressions into smaller subexpressions. You need to add the
empty transitions to complete each step.
As you are converting a regular expression to an NFA, write down the
intermediate expressions as a note on the JFLAP screen: use the
selection tool (the one that you use to mark initial and final
states), right-click anywhere on the JFLAP screen, and choose "add
note". For instance, if you are breaking down an expression
00+11
into 00
and 11
, write
00+11 -> 00, 11
.
Below are two regular expressions to convert:
- ((0+1)0)*
- (00)*+(10)*
Please export and submit your NFAs.
Task 2: Java regular expressions (20 points)
Study the Java
regular expressions tutorial (ignore the Test Harness section, we
use our own testing class). Note that instead of using the
Pattern and Matcher classes directly, you will be using the class RegExTester that
provides methods for
searching, splitting, and replacing strings based on regular
expressions. Study examples in main
in that class.
Important: by default regular expressions will
find a matching sequence within the given input; they do not match
the entire input. For instance, a regular expression "DFA" will find a
match in an input "DFAs are cool".
Also important: Java strings use \ as a special
character. Therefore you need \\ for predefined regex classes,
e.g. "\\d+" matches one or more digit. See a link to more predefined
classes in question 2 below.
Your tasks are as follows. Assume case-insensitive matches, unless
specified otherwise.
- Find all occurrences of letter combinations "dfa" and "nfa" in a
text.
- Find all integer numbers (i.e. sequences of digits with no other
characters) in a text. Use a predefined class \d to match a single
digit (see example here: http://java.sun.com/docs/books/tutorial/essential/regex/pre_char_classes.html
). Ignore the negative sign.
- Find all negative integer numbers, i.e. numbers preceded by a - sign
- Find all words that start with a letter t (hint: use boundary
matches http://java.sun.com/docs/books/tutorial/essential/regex/bounds.html
- Find all words in a text that have letters t and/or i in the them
(in any order)
- Use the doRegExSplit to split a string into items separated by |
- Use the doRegExReplace method to replace all occurrences of
"today" by "yesterday".
Make sure to submit your code (with some method calls commented out) and a copy of your test data for each regular expression (as a separate file or in comments).
What to submit
- Submit your JFLAP files as attachments, CC your group. Make sure
to submit your DFA
files (as .jff) and your input data (as .txt). Make sure to follow the
naming requirements! Make it clear which
data refers to which automaton.
CSci 3501
course web site.