LING/C SC/PSYC 438/538

LING/C SC/PSYC 438/538 Lecture 3 8/30 Sandiway Fong

Administrivia • Homework out today • change: due next Wednesday midnight • (Monday being Labor Day) • Reading reminder • Chapter 2 of JM.. we’ll be using Perl here

Quiz from Lecture 1 • Discussion (Quiz not handed back) • Is the word spoilsport an example of compositional semantics or not? Explain your answer. idioms contrasted with compositional e.g. spoilsmanvs. blackboard • Re: human language processing vs. machine models of language Did the authors cite any examples of this in chapter 1?

Perl Week • Tutorial contd… • http://perldoc.perl.org/perlintro.html • from arrays onwards …. • Philosophy: Natural Language Principles in Perl • If a language is designed so that you can ``learn as you go'', then the expectation is that everyone is learning, and that's okay. • http://www.wall.org/~larry/natural.html

Perl Week

Perl Week • Notes on arrays and hashes • Arrays are indexed from 0,1,2,3… • Hashes are like arrays with user-defined indexing (aka associative array or hash table) • Initialization (round brackets and commas) • @a = (“zero”, “one”, “two”, “three”, “four”); • %h = (“zero”, 0, “one”, 1, “two”, 2, “three”, 3, “four”, 4); (key/value pairs) • Access (square brackets vs. curly braces) • $a[1] “one” • $h{zero} 0 • Output • print @a zeroonetwothreefour • print “@a” zero one two three four • print %h three3one1zero0two2four4 (note: different order) • print “%h” %h

Perl Week • Conditionals • if ( @a < 10 ) { print “Small array\n” } else {print “Big array\n” } • Note: @a here is a scalar = size of array • unless (@a > 10) { print “@a\n” } • Note: if size of array a is ≤ 10, it prints the contents of array a • Looping • %fruits = ("apple", "green", "orange", "orange", "lemon", "yellow"); • foreach $fruit (keys %fruits) { print $fruit, " => ", $fruits{$fruit}, "\n” } gives output: • lemon => yellow • apple => green • orange => orange • Note: apparently here • keys %fruits = (“lemon” “apple” “orange”) is an array

Perl Week • Example: • the following program prints Equal! • == is the numeric equality comparison operator • my $one_string = “1”; • my $one_number = 1; • if ($one_string == $one_number) { • print “Equal!\n” • } else { • print “Different!\n” • } • Example: • the following program prints 3 is my number • . is the string concatenation operator • my @a = (one, two, three); • my $string = @a . “ is my number”; • print “$string\n”; Perl features implicit coercion of data types

Lecture 3 Homework • Due nextWednesday(see lecture 1 for the rules on submissions) • One file only total please! • Question 1: 438 and 538 (7 points) • Given • @sentence1 = (I, saw, the, the, cat, on, the, mat); • @sentence2 = (the, cat, sat, on, the, mat); • Write a simple Perl program which detects repeated words (many spell checker/grammar programs have this capability) • It should print a message stating the repeated word and its position if one exists • e.g. word 3 “the” is repeated in the case of sentence1 • No repeated words found in the case of sentence2 • note: output multiple messages if there are multiple repeated words • Hint: use a loop • Submit your Perl code and show examples of your program working

Lecture 3 Homework • Question 2: 438 and 538 (3 points) • Describe what would it take to stop a repeated word program from flagging legitimate examples of repeated words in a sentence • (No spell checker/grammar program that I know has this capability) • Examples of legitimately repeated words: • I wish that that question had an answer • Because he had had too many beers already, he skipped the Friday office happy hour

Lecture 3 Homework • Question 3: 538 (10 points), (438 extra credit) • Write a simple Perl program that outputs word frequencies for a sentence • E.g. given • @sentence1 = (I, saw, the, cat, on, the, mat, by, the, saw, table); • output a summary that looks something like: • the occurs 4 times • saw occurs twice • I, car, mat, on, by, table occurs once only • Hint: build a hash keyed by word with value frequency • Submit your Perl code and show examples of your program working

LING/C SC/PSYC 438/538