1. LING/C SC/PSYC 438/538
Lecture 19
Sandiway Fong

2. Today's Topics Homework 7 Review We will start to write grammars today
Quick Homework 8: install SWI-Prolog for next time
(no need to submit anything)

3. Homework 8: Install SWI Prolog
Install on your laptop (Mac or PC0:
prolog.org/build/Debian.html
sudo apt-add-repository ppa:swi-prolog/stable
sudo apt-get update
sudo apt-get install swi-prolog

4. Homework 8: Install SWI Prolog
Mac problems:
option-click on application

5. Homework 8: Install SWI Prolog
Alternative to the OSX application
port install swi-prolog
Yet another one is Homebrew

6. Homework 7 Review
Question 1: convert this 4-state NDFSA into a deterministic FSA
How many states does the DFSA have?
Σ = {0, 1}
double circle = final state
initial state = A
comma = disjunction

7. Homework 7 Review
Question 1: this 4-state NDFSA = an 8-state deterministic FSA

8. Homework 7 Review Question 2: Find a regex for this machine
Step 1: eliminate state D

9. Homework 7 Review (01)*01?([01]1*01)*([01]1*01(01)*01?([01]1*01)*)*
Step 2a: eliminate state B:
(01)*01?([01]1*01)*([01]1*01(01)*01?([01]1*01)*)*
Step 2b: eliminate state C:
(0|0[01]1*0)(1[01]1*0)*(1(0|0[01]1*0)(1[01]1*0)*)*

10. Homework 7 Review
Question 3: implement the DFSA in Perl or Python

11. Homework 7 Review

12. Homework 7 Review
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ling538-18$ python3 hw7-3.py

13. Homework 7 Review Question 4: implement the regex in Perl or Python
NO_B
NO_C

14. Homework 7 Review

15. Homework 7 Review

16. Homework 7 Review
for i in sigma/sigma[0-2][0-9].txt; do python3 hw7-3f.py $i; done
for i in sigma/sigma[0-2][0-9].txt; do perl hw7- 4f.perl $i; done
2: 1
16384: 1450
4: 1
32768: 2578
8: 2
65536: 4585
16: 5
131072: 8155
32: 8
262144: 14503
64: 14
524288: 25793
128: 26
: 45873
256: 46
: 81584
512: 81 :
1024: 145 :
2048: 258 :
4096: 458 :
8192: 815
2: 1
16384: 1450
4: 1
32768: 2578
8: 2
65536: 4585
16: 5
131072: 8155
32: 8
262144: 14503
64: 14
524288: 25793
128: 26
: 45873
256: 46
: 81584
512: 81 :
1024: 145 :
2048: 258 :
4096: 458 :
8192: 815
real 2m50.567s
user 2m47.246s
sys 0m3.196s
real 2m54.513s
user 2m52.142s
sys 0m2.204s

17. regexper.com

18. Homework 7 Review
Question 5: based on your testing, can you succinctly describe the language accepted in English?
Begins with a zero
No more than three zeros in a row

19. Control-D (EOF) to terminate.
SWI Prolog
every command ends in a period
case sensitive: variables begin with an uppercase letter
Control-D (EOF) to terminate.
halt.

20. SWI Prolog Cheatsheet At the prompt ?- Anytime Everything typed at the
prompt must end in a period.
At the prompt ?-
halt.
listing. listing(name). more useful
[filename]. loads filename.pl
trace (step through derivation, hit return)
notrace.
debug.
nodebug. turn off debugger
spy(name). spy on predicate name
pwd print working directory
working_directory(_,Y). switch directories to Y
Anytime
^C (then a(bort) or h(elp) for other options)

21. Example Learn Prolog Now! Notation: Data structures: \+ negation
, conjunction
; disjunction
:- if
Facts:
predicate(arguments).
Rules:
p(Args) :- q(Args) ,.., r(Args).
Data structures:
list: [a,..b]
empty list: []
head/tail: [h|List]
Atom:
name, number
Term:
functor(arguments)
arguments:
comma-separated terms/atoms
Learn Prolog Now!
P. Blackburn, J. Bos & K. Striegnitz

22. Prolog Recursion Example (factorial): In Prolog:
0! = 1
n! = n * (n-1)! for n>0
In Prolog:
factorial(0,1).
factorial(N,NF) :- M is N-1, factorial(M,MF), NF is N * MF.
Problem: infinite loop
Fix: 2nd case only applies to numbers > 0
factorial(N,NF) :- N>0, M is N-1, factorial(M,MF), NF is N * MF.
Prolog built-in:
X is <math expression>
Run
?- factorial(5,X).
(hit ; for more answers)

23. Prolog Recursion Example: Σ={0,1}, enumerate Σ* sigma(0). sigma(1).…
Example: Σ={0,1}, enumerate Σ*
sigma(0).
sigma(1).
sigmas([]).
sigmas([X|L]) :- sigmas(L), sigma(X).
Run (hit ; for more answers)
?- sigmas(L).