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" and Philosophy calls it "G83.2296"
6 The seminar meets in spring 2015 on Thursdays from 4 until a bit before 7 (with a short break in the middle), in
7 the Linguistics building at 10 Washington Place, in room 103 (front of the first floor).
10 One student session will be held every Wednesday from 3-4 on the
11 fourth floor at 10 Washington Place.
17 This wiki will be undergoing lots of changes throughout the semester, and particularly in these first few days as we get it set up, migrate over some of the content from the previous time
18 we taught this course, and iron out various technical wrinkles. Please be patient.
20 If you've eager to learn, though, you don't have to wait on us to be ready to serve you. You can go look at the [archived first version](http://lambda1.jimpryor.net) of this course. Just keep in mind that
21 the text and links there haven't been updated.
23 As we mentioned in class, if you're following the course and would like to be emailed occasionally, send an email to <mailto:jim.pryor@nyu.edu>, saying "lambda" in the subject line. Most often, we will just post announcements to this website, rather than emailing you. But occasionally an email might be more appropriate.
25 As we mentioned in class, we're also going to schedule a session to discuss the weekly homeworks. If you'd like to participate in this, please complete [this Doodle poll](http://doodle.com/7xrf4w8xq4i9e5za). It asks when you are available on Tuesdays and Wednesdays.
30 The goal of this seminar is to introduce concepts and techniques from
31 theoretical computer science and show how they can provide insight
32 into established philosophical and linguistic problems.
34 This is not a seminar about any particular technology or software.
36 Rather, it's about a variety of conceptual/logical ideas that have been
37 developed in computer science and that linguists and philosophers ought to
38 know, or may already be unknowingly trying to reinvent.
40 Philosphers and linguists tend to reuse the same familiar tools in
41 ever more (sometime spectacularly) creative ways. But when your only
42 hammer is classical logic, every problem looks like modus ponens. In
43 contrast, computer scientists have invested considerable ingenuity in
44 studying tool design, and have made remarkable progress.
46 "Why shouldn't I reinvent some idea X for myself? It's intellectually
47 rewarding!" Yes it is, but it also takes time you might have better
48 spent elsewhere. After all, you can get anywhere you want to go by walking, but you can
49 accomplish more with a combination of walking and strategic subway
52 More importantly, the idiosyncrasies of your particular
53 implementation may obscure what's fundamental to the idea you're
54 working with. Your implementation may be buggy in corner cases you
55 didn't think of; it may be incomplete and not trivial to generalize; its
56 connection to existing literature and neighboring issues may go
57 unnoticed. For all these reasons you're better off understanding the
60 The theoretical tools we'll be introducing aren't very familiar to
61 everyday programmers, but they are prominent in academic computer science,
62 especially in the fields of functional programming and type theory.
64 Of necessity, this course will lay a lot of logical groundwork. But throughout
65 we'll be aiming to mix that groundwork with real cases
66 in our home subjects where these tools play central roles.
69 course is to enable you to make these tools your own; to have enough
70 understanding of them to recognize them in use, use them yourself at least
71 in simple ways, and to be able to read more about them when appropriate.
74 Once we get up and running, the central focii of the course will be
75 **continuations**, **types**, and **monads**. One of the on-going themes will
76 concern evaluation order and issues about how computations (inferences,
77 derivations) unfold in (for instance) time. The key analytic technique is to
78 form a static, order-independent model of a dynamic process. We'll be
79 discussing this in much more detail as the course proceeds.
81 The logical systems we'll be looking at include:
83 * the pure/untyped lambda calculus
85 * the simply-typed lambda calculus
86 * polymorphic types with System F
87 * some discussion of dependent types
88 * if time permits, "indeterministic" or "preemptively parallel" computation and linear logic
92 recursion using the Y-combinator
93 evaluation-order stratgies
94 normalizing properties
95 the Curry-Howard isomorphism(s)
96 monads in category theory and computation
99 ## Who Can Participate? ##
101 The course will not presume previous experience with programming. We
102 will, however, discuss concepts embodied in specific programming
103 languages, and we will encourage experimentation with running,
104 modifying, and writing computer programs.
106 The course will not presume lots of mathematical or logical background, either.
107 However, it will demand a certain amount of comfort working with such material; as a result,
108 it will not be especially well-suited to be a first graduate-level course
109 in formal semantics or philosophy of language. If you have concerns about your
110 background, come discuss them with us.
113 This class will count as satisfying the logic requirement for Philosophy
114 PhD students; however if this would be your first or only serious
115 engagement with graduate-level formal work you should consider
116 carefully, and must discuss with us, (1) whether you'll be adequately
117 prepared for this course, and (2) whether you'd be better served by
118 taking a logic course (at a neighboring department, or at NYU next year)
119 with a more canonical syllabus.
122 Faculty and students from outside of NYU Linguistics and Philosophy are welcome
123 to audit, to the extent that this coheres well with the needs of our local
127 ## Recommended Software ##
129 During the course, we'll be encouraging you to try out various things in Scheme
130 and Caml, which are prominent *functional programming languages*. We'll explain
131 what that means during the course.
133 * **Scheme** is one of two major dialects of *Lisp*, which is a large family
134 of programming languages. Scheme
135 is the more clean and minimalistic dialect, and is what's mostly used in
137 Scheme itself has umpteen different "implementations", which share most of
138 their fundamentals, but have slightly different extensions and interact with
139 the operating system differently. One major implementation used to be called
140 PLT Scheme, and has just in the past few weeks changed their name to Racket.
141 This is what we recommend you use. (If you're already using or comfortable with
142 another Scheme implementation, though, there's no compelling reason to switch.)
144 Racket stands to Scheme in something like the relation Firefox stands to HTML.
146 * **Caml** is one of two major dialects of *ML*, which is another large
147 family of programming languages. Caml has only one active implementation,
148 OCaml, developed by the INRIA academic group in France.
150 * Those of you with some programming background may have encountered a third
151 prominent functional programming language, **Haskell**. This is also used a
152 lot in the academic contexts we'll be working through. Its surface syntax
153 differs from Caml, and there are various important things one can do in
154 each of Haskell and Caml that one can't (or can't as easily) do in the
155 other. But these languages also have a lot in common, and if you're
156 familiar with one of them, it's not difficult to move between it and the
160 <a name=installing></a>
161 [[How to get the programming languages running on your computer]]
163 [[Family tree of functional programming languages]]
165 [[Translating between OCaml Scheme and Haskell]]
167 ## What is Functional Programming? ##
169 Here's a [survey conducted at Microsoft](http://research.microsoft.com/apps/pubs/default.aspx?id=141506) asking programmers what they understand "functional programming" to be. Don't take their responses to be authoritative... this is a just a "man in the street" (seat?) poll.
171 Read more about the [uptake of Haskell](http://steve-yegge.blogspot.com/2010/12/haskell-researchers-announce-discovery.html) among programmers in the street.
174 ## Recommended Books ##
176 It's not *mandatory* 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. We especially recommend the first three of them.
178 * *An Introduction to Lambda Calculi for Computer Scientists*, by Chris
179 Hankin, currently $18 paperback on
180 [Amazon](http://www.amazon.com/dp/0954300653).
182 * *The Little Schemer, Fourth Edition*, by Daniel P. Friedman and Matthias
183 Felleisen, currently $29 paperback on [Amazon](http://www.amazon.com/exec/obidos/ASIN/0262560992).
184 This is a classic text introducing the gentle art of programming, using the
185 functional programming language Scheme. Many people love this book, but it has
186 an unusual dialog format that is not to everybody's taste. **Of particular
187 interest for this course** is the explanation of the Y combinator, available as
188 a free sample chapter [at the MIT Press web page for the
189 book](http://www.ccs.neu.edu/home/matthias/BTLS/).
191 * *The Seasoned Schemer*, also by Daniel P. Friedman and Matthias Felleisen, currently $29 paperback
192 on [Amazon](http://www.amazon.com/Seasoned-Schemer-Daniel-P-Friedman/dp/026256100X). This is a sequel to The Little Schemer, and it focuses on mutation and continuations in Scheme. We will be covering those topics in the second half of the course.
194 * *The Little MLer*, by Matthias Felleisen and Daniel P. Friedman, currently $31 paperback / $29 kindle
195 on [Amazon](http://www.amazon.com/Little-MLer-Matthias-Felleisen/dp/026256114X).
196 This covers much of the same introductory ground as The Little Schemer, but
197 this time in a dialect of ML. It doesn't use OCaml, the dialect we'll be working with, but instead another dialect of ML called SML. The syntactic differences between these languages is slight.
198 ([Here's a translation manual between them](http://www.mpi-sws.org/~rossberg/sml-vs-ocaml.html).)
199 Still, that does add an extra layer of interpretation, and you might as well just use The Little Schemer instead. Those of you who are already more comfortable with OCaml (or with Haskell) than with Scheme might consider working through this book instead of The Little Schemer; for the rest of you, or those of you who *want* practice with Scheme, go with The Little Schemer.
201 * Another good book covering the same ground as the Hankin book, but
202 more thoroughly, and in a more mathematical style, is *Lambda-Calculus and Combinators:
203 an Introduction*, by J. Roger Hindley and Jonathan P. Seldin, currently $74 hardback / $65 kindle on [Amazon](http://www.amazon.com/dp/0521898854).
204 This book is substantial and though it doesn't presuppose any specific mathematical background knowledge, it will be a good choice only if you're already comfortable reading advanced math textbooks.
205 If you choose to read both the Hankin book and this book, you'll notice the authors made some different
206 terminological/notational choices. At first, this makes comprehension slightly slower,
207 but in the long run it's helpful because it makes the arbitrariness of those choices more salient.
209 * Another good book, covering some of the same ground as the Hankin, and the Hindley & Seldin, but delving deeper into typed lambda calculi, is *Types and Programming Languages*, by Benjamin Pierce, currently $77 hardback / $68 kindle on [Amazon](http://www.amazon.com/dp/0262162091). This book has many examples in OCaml.
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