LING/C SC/PSYC 438/538. Lecture 4 Sandiway Fong

Transcription

1 LING/C SC/PSYC 438/538 Lecture 4 Sandiway Fong

2 Administrivia Last Time: Quick Homework 1 (you should have received an back from me) Today's class: Quick Homework 1 Review continue with perlintro with a dash of python

3 Q1: What's supposed to be funny about this? Q2: Run the 1 st sentence on the Berkeley Parser (from Quick Quiz 1). Critique the parse. Q3: Run the 1 st sentence on the Google Parser. Critique the dependency parse. (

4 Facebook Joke relies on the the human ability to flexibly attach PPs. Also, there could be a garden path here: preferred attachment site might be to lowest (most recent) VP.

5 Berkeley Parser Not a good parse: why? subject of play can't be interpreted as the kids A constructive question: can we force the Berkeley parser to give us the syntax we want?

6 Quirk: no period here! Assume unexpressed subject is the speaker, i.e. [ S [ NP PRO][ VP [ VBG V-ing] ]]

7 Move the PP with an adult beverage earlier in the sentence. result is high attachment to sitting. Unfortunately, watching the kids play now modifies an adult beverage.

8 Move the PP with an adult beverage ahead of in the sun. The VP watching the kids modifies the sun. What is the intended subject of play here?

9 Interpret unexpressed subject as the Speaker (of the sentence)

10

11 Problematic: looks like the VP modifies the NP

12

13 Change of PP attachment location Preposition with: accompaniment with cf. instrument with Can we force high attachment?

14 High attachment achieved!

15

16 Dependency Relations List of universal dependencies (v2): Relevant relations: ccomp: clausal complement xcomp: open clausal complement (no explicit subject) pobj (not V2): prepositional object

17 World and word knowledge adult beverage: not defined in a dictionary semantic compositionality at work: a beverage restricted to adults kid vs. adult: WordNet (taxonomy and semantic relations between word senses): adult#n#1 antonym of juvenile#n#1 hypernym of kid#n#1

18 Google search

19 perlintro Notes from the tutorial: semicolon (;) is not always necessary Command separator semantics vs. end of command (termination) token Best practice? Terminate every command with a semicolon Variable types: Every variable type has its own namespace. This means that $foo are two different variables. It also means that $foo[1] is a part not a part of $foo. This may seem a bit weird, but that's okay, because it is weird.

20 Perl Variable Prefixation Reading Perl code (perldata) aloud: Larry Wall was a linguist The '$' symbol works semantically like the English word "the" in that it indicates a single value is expected. Entire arrays (and slices of arrays and hashes) are denoted by '@', which works much like the word "these" or "those" does in English, in that it indicates multiple values are expected. Also: Entire hashes are denoted by '% (no translation) In addition, subroutines are named with an initial '&', though this is optional when unambiguous, just as the word "do" is often redundant in English.

21 Perl Arrays Arrays: Idea: list of scalars like a simple ordered list (cf. Python lists) access by index: 0,1,2, negative indices count from the end A note on output: zeroonetwothreefour zero one two three four controlled by system variable $" default value: a space

22 perlintro: Perl Arrays like a simple ordered list (in Python, we use a list) = (,, ) (round brackets; comma separator) Python: array = [,, ] Access: $ARRAY[ INDEX] Python: array[index] Index of last element: $#array Python: array[-1] (zero-indexed; negative indices ok; slices ok) (a scalar)

23 perlintro: Perl Arrays like a simple ordered list (in Python, we use a list) = number of elements in scalar context Python (no coercion): len(array) Built-in functions: $ELEMENT; $ELEMENT, $OFFSET, $LENGTH, $ELEMENT $ELEMENT above can Python: array.sort(), array.reverse(), NO push (use array.append() instead), array.pop(), No shift/unshift etc (command line arguments) (sub(routine) arguments)

24 perlintro: Perl Arrays Similar to pop/push, but operates at the left end of the array Python doesn't have these defined but can be simulated via slicing and concatenation: array[1:] list + array

25 perlintro: Perl Arrays