1 # Seminar in Semantics / Philosophy of Language #
3 or: **What Philosophers and Linguists Can Learn From Theoretical Computer Science But Didn't Know To Ask**
5 This course will be co-taught by [Chris Barker](http://homepages.nyu.edu/~cb125/) and [Jim Pryor](http://www.jimpryor.net/). Linguistics calls it "G61.3340-002" and Philosophy calls it "G83.2296-001."
10 * The seminar meets on Mondays from 4-6, in
11 the Linguistics building at 10 Washington Place, in room 104 (back of the first floor).
15 * One student session will be held every Wednesday from 3-4. The other will
16 be arranged to fit the schedule of those who'd like to attend but can't
17 make the Wednesday time. (We first proposed Tuesdays from 11-12, but this
18 time turns out not to be so helpful.) If you're one of the students who
19 wants to meet for Q&A at some other time in the week, let us know.
21 You should see the student sessions as opportunities to clear up lingering
22 issues from material we've discussed, and help get a better footing for what
23 we'll be doing the next week. It would be smart to make a serious start on that
24 week's homework, for instance, before the session.
26 * There is now a [[lambda evaluator]] you can use in your browser (no need to
27 install any software). It can help you check whether your answer to some of the
28 homework questions works correctly.
30 There is also now a [library](/lambda_library) of lambda-calculus
31 arithmetical and list operations, some relatively advanced.
33 An evaluator with the definitions used for homework 3
34 preloaded is available at [[assignment 3 evaluator]].
36 * Henceforth, unless we say otherwise, every homework will be "due" by
37 Sunday morning after the Monday seminar in which we refer to it.
38 (Usually we'll post the assignment shortly before the seminar, but don't
39 rely on this.) However, for every assignment there will be a "grace
40 period" of one further week for you to continue working on it if you
41 have trouble and aren't able to complete the assignment to your
42 satisfaction by the due date. You shouldn't hesitate to talk to us---or
43 each other!---about the assignments when you do have trouble. We don't
44 mind so much if you come across answers to the assignment when browsing
45 the web, or the Little Schemer book, or anywhere. So long as you can
46 reason yourself through the solutions and experience for yourself the
49 We reserve the privilege to ruthlessly require you to
50 explain your solutions in conversations at any point, in section or in
53 You should always *aim* to complete the assignments by the "due" date,
54 as this will fit best with the progress of the seminar. Let's take
55 assignment 3 to be "due" on Sunday Oct 3 (the date of this
56 announcement), but as we announced last week in seminar, you can take up
57 until this coming Sunday to complete it. If you need to. Try to complete
58 it, and get assistance completing it if you need it, sooner.
60 * We'll shortly be posting another assignment, assignment 4, which will be
61 "due" on the Sunday before our next seminar. That is, on Sunday Oct 17.
62 (There's no seminar this coming Monday.)
64 The assignments will tend to be quite challenging. Again, you should by
65 all means talk amongst yourselves, and to us, about strategies and
66 questions that come up when working through them.
68 We will not always be able to predict accurately which problems are
69 easy and which are hard. If we misjudge, and choose a problem that is
70 too hard for you to complete to your own satisfaction, it is still
71 very much worthwhile (and very much appreciated) if you would explain
72 what is difficult, what you tried, why what you tried didn't work, and
73 what you think you need in order to solve the problem.
78 To play around with a **typed lambda calculus**, which we'll look at later
79 in the course, have a look at the [Penn Lambda Calculator](http://www.ling.upenn.edu/lambda/).
80 This requires installing Java, but provides a number of tools for evaluating
81 lambda expressions and other linguistic forms. (Mac users will most likely
82 already have Java installed.)
86 ## Lecture Notes and Assignments ##
88 (13 Sept) Lecture notes for [[Week1]]; [[Assignment1]].
90 Topics: Applications; Basics of Lambda Calculus; Comparing Different Languages
92 (20 Sept) Lecture notes for [[Week2]]; [[Assignment2]].
94 Topics: Reduction and Convertibility; Combinators; Evaluation Strategies and Normalization; Decidability; Lists and Numbers
96 (27 Sept) Lecture notes for [[Week3]]; [[Assignment3]].
98 Topics: Recursion with Fixed Point Combinators
100 (4 Oct) Lecture notes for Week 4
102 <!-- Introducing the notion of a "continuation", which technique we'll now already have used a few times
108 ##[[Offsite Reading]]##
110 There's lots of links here already to tutorials and encyclopedia entries about many of the notions we'll be dealing with.
114 ## Course Overview ##
116 The goal of this seminar is to introduce concepts and techniques from
117 theoretical computer science and show how they can provide insight
118 into established philosophical and linguistic problems.
120 This is not a seminar about any particular technology or software.
121 Rather, it's about a variety of conceptual/logical ideas that have been
122 developed in computer science and that linguists and philosophers ought to
123 know, or may already be unknowingly trying to reinvent.
125 Philosphers and linguists tend to reuse the same familiar tools in
126 ever more (sometime spectacularly) creative ways. But when your only
127 hammer is classical logic, every problem looks like modus ponens. In
128 contrast, computer scientists have invested considerable ingenuity in
129 studying tool design, and have made remarkable progress.
131 "Why shouldn't I reinvent some idea X for myself? It's intellectually
132 rewarding!" Yes it is, but it also takes time you might have better
133 spent elsewhere. After all, you can get anywhere you want to go by walking, but you can
134 accomplish more with a combination of walking and strategic subway
137 More importantly, the idiosyncrasies of your particular
138 implementation may obscure what's fundamental to the idea you're
139 working with. Your implementation may be buggy in corner cases you
140 didn't think of; it may be incomplete and not trivial to generalize; its
141 connection to existing literature and neighboring issues may go
142 unnoticed. For all these reasons you're better off understanding the
145 The theoretical tools we'll be introducing aren't very familiar to
146 everyday programmers, but they are prominent in academic computer science,
147 especially in the fields of functional programming and type theory.
149 Of necessity, this course will lay a lot of logical groundwork. But throughout
150 we'll be aiming to mix that groundwork with real cases
151 in our home subjects where these tools play central roles. Our aim for the
152 course is to enable you to make these tools your own; to have enough
153 understanding of them to recognize them in use, use them yourself at least
154 in simple ways, and to be able to read more about them when appropriate.
156 Once we get up and running, the central focii of the course will be
157 **continuations**, **types**, and **monads**. One of the on-going themes will
158 concern evaluation order and issues about how computations (inferences,
159 derivations) unfold in (for instance) time. The key analytic technique is to
160 form a static, order-independent model of a dynamic process. We'll be
161 discussing this in much more detail as the course proceeds.
163 The logical systems we'll be looking at include:
165 * the pure/untyped lambda calculus
166 * combinatorial logic
167 * the simply-typed lambda calculus
168 * polymorphic types with System F
169 * some discussion of dependent types
170 * if time permits, "indeterministic" or "preemptively parallel" computation and linear logic
175 recursion using the Y-combinator
176 evaluation-order stratgies
177 normalizing properties
178 the Curry-Howard isomorphism(s)
179 monads in category theory and computation
182 ## Who Can Participate? ##
184 The course will not presume previous experience with programming. We
185 will, however, discuss concepts embodied in specific programming
186 languages, and we will encourage experimentation with running,
187 modifying, and writing computer programs.
189 The course will not presume lots of mathematical or logical background, either.
190 However, it will demand a certain amount of comfort working with such material; as a result,
191 it will not be especially well-suited to be a first graduate-level course
192 in formal semantics or philosophy of language. If you have concerns about your
193 background, come discuss them with us.
195 This class will count as satisfying the logic requirement for Philosophy
196 PhD students; however if this would be your first or only serious
197 engagement with graduate-level formal work you should consider
198 carefully, and must discuss with us, (1) whether you'll be adequately
199 prepared for this course, and (2) whether you'd be better served by
200 taking a logic course (at a neighboring department, or at NYU next year)
201 with a more canonical syllabus.
204 Faculty and students from outside of NYU Linguistics and Philosophy are welcome
205 to audit, to the extent that this coheres well with the needs of our local
209 ## Recommended Software ##
211 During the course, we'll be encouraging you to try out various things in Scheme
212 and Caml, which are prominent *functional programming languages*. We'll explain
213 what that means during the course.
215 * **Scheme** is one of two major dialects of *Lisp*, which is a large family
216 of programming languages. Scheme
217 is the more clean and minimalistic dialect, and is what's mostly used in
219 Scheme itself has umpteen different "implementations", which share most of
220 their fundamentals, but have slightly different extensions and interact with
221 the operating system differently. One major implementation used to be called
222 PLT Scheme, and has just in the past few weeks changed their name to Racket.
223 This is what we recommend you use. (If you're already using or comfortable with
224 another Scheme implementation, though, there's no compelling reason to switch.)
226 Racket stands to Scheme in something like the relation Firefox stands to HTML.
228 * **Caml** is one of two major dialects of *ML*, which is another large
229 family of programming languages. Caml has only one active implementation,
230 OCaml, developed by the INRIA academic group in France.
232 * Those of you with some programming background may have encountered a third
233 prominent functional programming language, **Haskell**. This is also used a
234 lot in the academic contexts we'll be working through. Its surface syntax
235 differs from Caml, and there are various important things one can do in
236 each of Haskell and Caml that one can't (or can't as easily) do in the
237 other. But these languages also have a lot in common, and if you're
238 familiar with one of them, it's not difficult to move between it and the
241 [[How to get the programming languages running on your computer]]
243 [[Family tree of functional programming languages]]
246 ## Recommended Books ##
248 It's not necessary to purchase these for the class. But they are good ways to get a more thorough and solid understanding of some of the more basic conceptual tools we'll be using.
250 * *An Introduction to Lambda Calculi for Computer Scientists*, by Chris
251 Hankin, currently $17 on
252 [Amazon](http://www.amazon.com/Introduction-Lambda-Calculi-Computer-Scientists/dp/0954300653).
254 * (Another good book covering the same ground as the Hankin book, but
255 more thoroughly, and in a more mathematical style, is *Lambda-Calculus and Combinators:
256 an Introduction*, by J. Roger Hindley and Jonathan P. Seldin. If you choose to read
257 both the Hankin book and this book, you'll notice the authors made some different
258 terminological/notational choices. At first, this makes comprehension slightly slower,
259 but in the long run it's helpful because it makes the arbitrariness of those choices more salient.)
262 * *The Little Schemer, Fourth Edition*, by Daniel P. Friedman and Matthias
263 Felleisen, currently $23 on [Amazon](http://www.amazon.com/exec/obidos/ASIN/0262560992).
264 This is a classic text introducing the gentle art of programming, using the
265 functional programming language Scheme. Many people love this book, but it has
266 an unusual dialog format that is not to everybody's taste. **Of particular
267 interest for this course** is the explanation of the Y combinator, available as
268 a free sample chapter [at the MIT Press web page for the
269 book](http://www.ccs.neu.edu/home/matthias/BTLS/).
271 * *The Seasoned Schemer*, also by Daniel P. Friedman and Matthias Felleisen, currently $28
272 on [Amazon](http://www.amazon.com/Seasoned-Schemer-Daniel-P-Friedman/dp/026256100X)
274 * *The Little MLer*, by Matthias Felleisen and Daniel P. Friedman, currently $27
275 on [Amazon](http://www.amazon.com/Little-MLer-Matthias-Felleisen/dp/026256114X).
276 This covers some of the same introductory ground as The Little Schemer, but
277 this time in ML. It uses another dialect of ML (called SML), instead of OCaml, but there are only
278 superficial syntactic differences between these languages. [Here's a translation
279 manual between them](http://www.mpi-sws.org/~rossberg/sml-vs-ocaml.html).
285 All wikis are supposed to have a [[SandBox]], so this one does too.
287 This wiki is powered by [[ikiwiki]].