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 is 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."
6 The seminar meets on Mondays from 4-6, in
7 the Linguistics building at 10 Washington Place, in room 104 (back of the first floor).
8 One student session will be held every Wednesday from 3-4 on the
9 fourth floor at 10 Washington Place.
13 * This is the time of the semester when some people start slipping
14 behind with the homework. Don't.
16 * We've added a page on [[Translating between OCaml Scheme and Haskell]]
18 [[Older Announcements]]
20 ##[[Lambda Evaluator]]##
22 Usable in your browser. It can help you check whether your answer to some of
23 the homework questions works correctly.
25 There is also now a [library](/lambda_library) of lambda-calculus
26 arithmetical and list operations, some relatively advanced.
29 ## Lecture Notes and Assignments ##
31 (13 Sept) Lecture notes for [[Week1]]; [[Assignment1]].
33 > Topics: [[Applications]], including [[Damn]]; Basics of Lambda Calculus; Comparing Different Languages
35 (20 Sept) Lecture notes for [[Week2]]; [[Assignment2]].
37 > Topics: Reduction and Convertibility; Combinators; Evaluation Strategies and Normalization; Decidability; [[Lists and Numbers]]
39 (27 Sept) Lecture notes for [[Week3]]; [[Assignment3]];
40 an evaluator with the definitions used for homework 3
41 preloaded is available at [[assignment 3 evaluator]].
43 > Topics: [[Evaluation Order]]; Recursion with Fixed Point Combinators
45 (4 Oct) Lecture notes for [[Week4]]; [[Assignment4]].
47 > Topics: More on Fixed Points; Sets; Aborting List Traversals; [[Implementing Trees]]
50 (18 Oct, 25 Oct) Lecture notes for [[Week5]] and [[Week6]]; [[Assignment5]].
52 > Topics: Types, Polymorphism, Unit and Bottom
54 (1 Nov) Lecture notes for [[Week7]]; [[Assignment6]].
56 > Topics: Monads; [[Reader Monad for Variable Binding]]; [[Reader Monad for Intensionality]]
58 (8 Nov) Lecture notes for [[Week8]].
60 > Topics: Reader Monad for Jacobson's Variable-Free Semantics
62 (15 Nov) Lecture notes for [[Week9]]; [[Assignment7]]. Everyone auditing in the class is encouraged to do this assignment, or at least work through the substantial "hints".
64 > Topics: Mutable Variables; Passing by Reference
66 (22 Nov) Lecture notes for [[Week10]]
68 > Topics: Calculator Improvements, including mutation
70 (30 Nov) Lecture notes for [[Week11]]; [[Assignment8]].
72 > Topics: [[Tree and List Zippers]]; [[Coroutines and Aborts]]; [[From List Zippers to Continuations]].
74 (6 Dec) Lecture notes for [[Week12]]
76 > Topics: [[List Monad as Continuation Monad]]; [[Manipulating Trees with Monads]]; ...
78 (13 Dec) Lecture notes for Week13
84 > Topics: Version 4 lists, Monads in Category Theory, Calculator Improvements
88 See [below](#installing) for how to get the programming languages running on your computer.
90 * Links for help [[learning Scheme]]
92 * Links for help [[learning OCaml]]
95 ##[[Offsite Reading]]##
97 There's lots of links here already to tutorials and encyclopedia entries about many of the notions we'll be dealing with.
101 ## Course Overview ##
103 The goal of this seminar is to introduce concepts and techniques from
104 theoretical computer science and show how they can provide insight
105 into established philosophical and linguistic problems.
107 This is not a seminar about any particular technology or software.
108 Rather, it's about a variety of conceptual/logical ideas that have been
109 developed in computer science and that linguists and philosophers ought to
110 know, or may already be unknowingly trying to reinvent.
112 Philosphers and linguists tend to reuse the same familiar tools in
113 ever more (sometime spectacularly) creative ways. But when your only
114 hammer is classical logic, every problem looks like modus ponens. In
115 contrast, computer scientists have invested considerable ingenuity in
116 studying tool design, and have made remarkable progress.
118 "Why shouldn't I reinvent some idea X for myself? It's intellectually
119 rewarding!" Yes it is, but it also takes time you might have better
120 spent elsewhere. After all, you can get anywhere you want to go by walking, but you can
121 accomplish more with a combination of walking and strategic subway
124 More importantly, the idiosyncrasies of your particular
125 implementation may obscure what's fundamental to the idea you're
126 working with. Your implementation may be buggy in corner cases you
127 didn't think of; it may be incomplete and not trivial to generalize; its
128 connection to existing literature and neighboring issues may go
129 unnoticed. For all these reasons you're better off understanding the
132 The theoretical tools we'll be introducing aren't very familiar to
133 everyday programmers, but they are prominent in academic computer science,
134 especially in the fields of functional programming and type theory.
136 Of necessity, this course will lay a lot of logical groundwork. But throughout
137 we'll be aiming to mix that groundwork with real cases
138 in our home subjects where these tools play central roles. Our aim for the
139 course is to enable you to make these tools your own; to have enough
140 understanding of them to recognize them in use, use them yourself at least
141 in simple ways, and to be able to read more about them when appropriate.
143 Once we get up and running, the central focii of the course will be
144 **continuations**, **types**, and **monads**. One of the on-going themes will
145 concern evaluation order and issues about how computations (inferences,
146 derivations) unfold in (for instance) time. The key analytic technique is to
147 form a static, order-independent model of a dynamic process. We'll be
148 discussing this in much more detail as the course proceeds.
150 The logical systems we'll be looking at include:
152 * the pure/untyped lambda calculus
153 * combinatorial logic
154 * the simply-typed lambda calculus
155 * polymorphic types with System F
156 * some discussion of dependent types
157 * if time permits, "indeterministic" or "preemptively parallel" computation and linear logic
162 recursion using the Y-combinator
163 evaluation-order stratgies
164 normalizing properties
165 the Curry-Howard isomorphism(s)
166 monads in category theory and computation
169 ## Who Can Participate? ##
171 The course will not presume previous experience with programming. We
172 will, however, discuss concepts embodied in specific programming
173 languages, and we will encourage experimentation with running,
174 modifying, and writing computer programs.
176 The course will not presume lots of mathematical or logical background, either.
177 However, it will demand a certain amount of comfort working with such material; as a result,
178 it will not be especially well-suited to be a first graduate-level course
179 in formal semantics or philosophy of language. If you have concerns about your
180 background, come discuss them with us.
182 This class will count as satisfying the logic requirement for Philosophy
183 PhD students; however if this would be your first or only serious
184 engagement with graduate-level formal work you should consider
185 carefully, and must discuss with us, (1) whether you'll be adequately
186 prepared for this course, and (2) whether you'd be better served by
187 taking a logic course (at a neighboring department, or at NYU next year)
188 with a more canonical syllabus.
191 Faculty and students from outside of NYU Linguistics and Philosophy are welcome
192 to audit, to the extent that this coheres well with the needs of our local
196 ## Recommended Software ##
198 During the course, we'll be encouraging you to try out various things in Scheme
199 and Caml, which are prominent *functional programming languages*. We'll explain
200 what that means during the course.
202 * **Scheme** is one of two major dialects of *Lisp*, which is a large family
203 of programming languages. Scheme
204 is the more clean and minimalistic dialect, and is what's mostly used in
206 Scheme itself has umpteen different "implementations", which share most of
207 their fundamentals, but have slightly different extensions and interact with
208 the operating system differently. One major implementation used to be called
209 PLT Scheme, and has just in the past few weeks changed their name to Racket.
210 This is what we recommend you use. (If you're already using or comfortable with
211 another Scheme implementation, though, there's no compelling reason to switch.)
213 Racket stands to Scheme in something like the relation Firefox stands to HTML.
215 * **Caml** is one of two major dialects of *ML*, which is another large
216 family of programming languages. Caml has only one active implementation,
217 OCaml, developed by the INRIA academic group in France.
219 * Those of you with some programming background may have encountered a third
220 prominent functional programming language, **Haskell**. This is also used a
221 lot in the academic contexts we'll be working through. Its surface syntax
222 differs from Caml, and there are various important things one can do in
223 each of Haskell and Caml that one can't (or can't as easily) do in the
224 other. But these languages also have a lot in common, and if you're
225 familiar with one of them, it's not difficult to move between it and the
228 <a name=installing></a>
229 [[How to get the programming languages running on your computer]]
231 [[Family tree of functional programming languages]]
233 [[Translating between OCaml Scheme and Haskell]]
236 ## Recommended Books ##
238 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.
240 * *An Introduction to Lambda Calculi for Computer Scientists*, by Chris
241 Hankin, currently $17 on
242 [Amazon](http://www.amazon.com/dp/0954300653).
244 * (Another good book covering the same ground as the Hankin book, but
245 more thoroughly, and in a more mathematical style, is *Lambda-Calculus and Combinators:
246 an Introduction*, by J. Roger Hindley and Jonathan P. Seldin, currently $52 on [Amazon](http://www.amazon.com/dp/0521898854). If you choose to read
247 both the Hankin book and this book, you'll notice the authors made some different
248 terminological/notational choices. At first, this makes comprehension slightly slower,
249 but in the long run it's helpful because it makes the arbitrariness of those choices more salient.)
251 * (Another good book, covering some of the same ground as the previous two, but also delving much deeper into typed lambda calculi, is *Types and Programming Languages*, by Benjamin Pierce, currently $61 on [Amazon](http://www.amazon.com/dp/0262162091). This book has many examples in OCaml.)
253 * *The Little Schemer, Fourth Edition*, by Daniel P. Friedman and Matthias
254 Felleisen, currently $23 on [Amazon](http://www.amazon.com/exec/obidos/ASIN/0262560992).
255 This is a classic text introducing the gentle art of programming, using the
256 functional programming language Scheme. Many people love this book, but it has
257 an unusual dialog format that is not to everybody's taste. **Of particular
258 interest for this course** is the explanation of the Y combinator, available as
259 a free sample chapter [at the MIT Press web page for the
260 book](http://www.ccs.neu.edu/home/matthias/BTLS/).
262 * *The Seasoned Schemer*, also by Daniel P. Friedman and Matthias Felleisen, currently $28
263 on [Amazon](http://www.amazon.com/Seasoned-Schemer-Daniel-P-Friedman/dp/026256100X)
265 * *The Little MLer*, by Matthias Felleisen and Daniel P. Friedman, currently $27
266 on [Amazon](http://www.amazon.com/Little-MLer-Matthias-Felleisen/dp/026256114X).
267 This covers some of the same introductory ground as The Little Schemer, but
268 this time in ML. It uses another dialect of ML (called SML), instead of OCaml, but there are only
269 superficial syntactic differences between these languages. [Here's a translation
270 manual between them](http://www.mpi-sws.org/~rossberg/sml-vs-ocaml.html).
276 All wikis are supposed to have a [[SandBox]], so this one does too.
278 This wiki is powered by [[ikiwiki]].