or: **What Philosophers and Linguists Can Learn From Theoretical Computer Science But Didn't Know To Ask**
-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."
+This course is co-taught by [Chris Barker](http://homepages.nyu.edu/~cb125/) and [Jim Pryor](http://www.jimpryor.net/). Linguistics calls it "LING-GA 3340" and Philosophy calls it "PHIL-GA 2296".
+The seminar meets in spring 2015 on Thursdays from 4 until a bit before 7 (with a short break in the middle), in
+the Linguistics building at 10 Washington Place, in room 103 (front of the first floor).
+
+<!--
+One student session will be held every Wednesday from XX-YY at WHERE.
+-->
## Announcements ##
-* The seminar meets on Mondays from 4-6, in
-the Linguistics building at 10 Washington Place, in room 104 (back of the first floor).
+* 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
+we taught this course, and iron out various technical wrinkles. Please be patient. When you sit down to read the wiki, it's a good idea to always hit "Refresh" in your browser to make sure you're reading the latest additions and refinements of the website. (Sometimes these will be tweaks, other times very substantial. Updates will happen at miscellaneous hours, sometimes many times in a given day.)
+
+ 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
+the text and links there haven't been updated. And/or you can get started on installing the software and ordering some of the books.
-<font color=red>
+* 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.
+
+* 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.
+
+<!--
+One student session will be held every Wednesday from XX-YY at WHERE.
-* One student session will be held every Wednesday from 3-4. The other will
-be arranged to fit the schedule of those who'd like to attend but can't
-make the Wednesday time. (We first proposed Tuesdays from 11-12, but this
-time turns out not to be so helpful.) If you're one of the students who
+For those who'd like to attend the section but can't make the
+Wednesday time: If you're one of the students who
wants to meet for Q&A at some other time in the week, let us know.
- You should see the student sessions as opportunities to clear up lingering
+You should see the student sessions as opportunities to clear up lingering
issues from material we've discussed, and help get a better footing for what
we'll be doing the next week. It would be smart to make a serious start on that
week's homework, for instance, before the session.
+-->
-* There is now a [[lambda evaluator]] you can use in your browser (no need to
-install any software). It can help you check whether your answer to some of the
-homework questions works correctly.
+* Here is information about [[How to get the programming languages running on your computer]].
- There is also now a [library](/lambda_library) of lambda-calculus
-arithmetical and list operations, some relatively advanced.
+* Here are Lecture notes for [[Week1]]; [[Assignment1]]. There are also some [[advanced notes|week1 advanced notes]].
- An evaluator with the definitions used for homework 3
-preloaded is available at [[assignment 3 evaluator]].
+ > Topics: Basics of Functional Programming
-* Henceforth, unless we say otherwise, every homework will be "due" by
-Sunday morning after the Monday seminar in which we refer to it.
+* Henceforth, unless we say otherwise, every homework will be "due" by
+Wednesday morning after the Thursday seminar in which we refer to it.
(Usually we'll post the assignment shortly before the seminar, but don't
rely on this.) However, for every assignment there will be a "grace
period" of one further week for you to continue working on it if you
reason yourself through the solutions and experience for yourself the
insights they embody.
- We reserve the privilege to ruthlessly require you to
+ We reserve the privilege to ruthlessly require you to
explain your solutions in conversations at any point, in section or in
class.
- You should always *aim* to complete the assignments by the "due" date,
-as this will fit best with the progress of the seminar. Let's take
-assignment 3 to be "due" on Sunday Oct 3 (the date of this
-announcement), but as we announced last week in seminar, you can take up
-until this coming Sunday to complete it. If you need to. Try to complete
-it, and get assistance completing it if you need it, sooner.
-
-* We'll shortly be posting another assignment, assignment 4, which will be
-"due" on the Sunday before our next seminar. That is, on Sunday Oct 17.
-(There's no seminar on Monday Oct 11.)
+ You should always *aim* to complete the assignments by the "due" date,
+as this will fit best with the progress of the seminar.
- The assignments will tend to be quite challenging. Again, you should by
+ The assignments will tend to be quite challenging. Again, you should by
all means talk amongst yourselves, and to us, about strategies and
questions that come up when working through them.
- We will not always be able to predict accurately which problems are
+ We will not always be able to predict accurately which problems are
easy and which are hard. If we misjudge, and choose a problem that is
too hard for you to complete to your own satisfaction, it is still
very much worthwhile (and very much appreciated) if you would explain
what is difficult, what you tried, why what you tried didn't work, and
what you think you need in order to solve the problem.
-</font>
-
-<!--
- To play around with a **typed lambda calculus**, which we'll look at later
- in the course, have a look at the [Penn Lambda Calculator](http://www.ling.upenn.edu/lambda/).
- This requires installing Java, but provides a number of tools for evaluating
- lambda expressions and other linguistic forms. (Mac users will most likely
- already have Java installed.)
--->
-
-
-## Lecture Notes and Assignments ##
-
-(13 Sept) Lecture notes for [[Week1]]; [[Assignment1]].
-
-Topics: Applications; Basics of Lambda Calculus; Comparing Different Languages
-
-(20 Sept) Lecture notes for [[Week2]]; [[Assignment2]].
-
-Topics: Reduction and Convertibility; Combinators; Evaluation Strategies and Normalization; Decidability; Lists and Numbers
-
-(27 Sept) Lecture notes for [[Week3]]; [[Assignment3]];
-an evaluator with the definitions used for homework 3
-preloaded is available at [[assignment 3 evaluator]].
-
-Topics: Recursion with Fixed Point Combinators
-
-(4 Oct) Lecture notes for Week 4
-
-<!-- Introducing the notion of a "continuation", which technique we'll now already have used a few times
--->
-
-[[Upcoming topics]]
-
-
-##[[Offsite Reading]]##
-
-There's lots of links here already to tutorials and encyclopedia entries about many of the notions we'll be dealing with.
-
-
## Course Overview ##
-The goal of this seminar is to introduce concepts and techniques from
+The overarching goal of this seminar is to introduce concepts and techniques from
theoretical computer science and show how they can provide insight
into established philosophical and linguistic problems.
ever more (sometime spectacularly) creative ways. But when your only
hammer is classical logic, every problem looks like modus ponens. In
contrast, computer scientists have invested considerable ingenuity in
-studying tool design, and have made remarkable progress.
+studying the design of their conceptual tools (among other things), and they've made much progress that we can benefit from.
"Why shouldn't I reinvent some idea X for myself? It's intellectually
rewarding!" Yes it is, but it also takes time you might have better
unnoticed. For all these reasons you're better off understanding the
state of the art.
-The theoretical tools we'll be introducing aren't very familiar to
+The theoretical tools we'll be introducing aren't part of the diet of most
everyday programmers, but they are prominent in academic computer science,
especially in the fields of functional programming and type theory.
Of necessity, this course will lay a lot of logical groundwork. But throughout
we'll be aiming to mix that groundwork with real cases
-in our home subjects where these tools play central roles. Our aim for the
+in our home subjects where these tools can (or already do, covertly) play central roles.
+
+Our aim for the
course is to enable you to make these tools your own; to have enough
understanding of them to recognize them in use, use them yourself at least
in simple ways, and to be able to read more about them when appropriate.
-Once we get up and running, the central focii of the course will be
-**continuations**, **types**, and **monads**. One of the on-going themes will
-concern evaluation order and issues about how computations (inferences,
-derivations) unfold in (for instance) time. The key analytic technique is to
-form a static, order-independent model of a dynamic process. We'll be
-discussing this in much more detail as the course proceeds.
+[[More about the topics and larger themes of the course|topics and themes]]
-The logical systems we'll be looking at include:
-
-* the pure/untyped lambda calculus
-* combinatorial logic
-* the simply-typed lambda calculus
-* polymorphic types with System F
-* some discussion of dependent types
-* if time permits, "indeterministic" or "preemptively parallel" computation and linear logic
-
-
-<!--
-Other keywords:
- recursion using the Y-combinator
- evaluation-order stratgies
- normalizing properties
- the Curry-Howard isomorphism(s)
- monads in category theory and computation
--->
## Who Can Participate? ##
in formal semantics or philosophy of language. If you have concerns about your
background, come discuss them with us.
-This class will count as satisfying the logic requirement for Philosophy
-PhD students; however if this would be your first or only serious
+If you hope to have the class satisfy the logic requirement for Philosophy PhD students, this needs to be discussed with us and approved in advance. If this would be
+your first or only serious
engagement with graduate-level formal work you should consider
carefully, and must discuss with us, (1) whether you'll be adequately
prepared for this course, and (2) whether you'd be better served by
-taking a logic course (at a neighboring department, or at NYU next year)
+taking a logic course
with a more canonical syllabus.
-
+This term you could take PHIL-GA 1003, [Logic for Philosophers](http://jdh.hamkins.org), offered by Joel Hamkins on Wednesdays 12-2.
Faculty and students from outside of NYU Linguistics and Philosophy are welcome
to audit, to the extent that this coheres well with the needs of our local
## Recommended Software ##
During the course, we'll be encouraging you to try out various things in Scheme
-and Caml, which are prominent *functional programming languages*. We'll explain
-what that means during the course.
-
-* **Scheme** is one of two major dialects of *Lisp*, which is a large family
+and OCaml. Occasionally we will also make remarks about Haskell. All three of these
+are prominent *functional programming languages*. The term "functional" here means they have
+a special concern with functions, not just that they aren't broken. But what precisely is
+meant by "functional" is somewhat fuzzy and even its various precisifications take some
+time to explain. We'll get clearer on this during the course. Another term used roughly the same as "functional"
+is "declarative." At a first pass, "functional" or "declarative" programming is primarily focused on complex
+expressions that get computationally evaluated to some (usually simpler) result. In class I gave the examples
+of `1+2` (which gets evaluated in arithmetic to `3`), `1+2 < 5` (which gets evaluated in arithmetic to a truth-value), and `1`
+(which gets evaluated in arithmetic to `1`). Also Google search strings, which get evaluated by Google servers to a
+list of links.
+
+The dominant contrasting class of programming languages (the great majority of what's used
+in industry) are called "imperatival" languages, meaning they have more to do with following a sequence of commands (generating what we
+called in class "side-effects", though sometimes what they're *alongside* is not that interesting, and all the focus is instead
+on the effects). Programming languages like C and Python and JavaScript and so on are predominantly of this sort.
+
+In truth, nothing that gets marketed as a "programming language" is really completely 100% functional/declarative, and even the
+languages I called "imperatival" will have some "functional" *fragments* (they evaluate `1+2` to `3`, also). So these labels aren't
+strictly exclusive. The labels are better thought of as concerning different
+*styles* or *idioms* of programming. Languages like Scheme and OCaml and especially Haskell get called "functional languages" because
+of the extent to which they emphasize, and are designed around those idioms. Languages like Python and JavaScript are sometimes themselves
+described as "more functional" than other languages, like C.
+
+
+In any case, here is some more context for the three languages we will be focusing on.
+
+* **Scheme** is one of two or three major dialects of *Lisp*, which is a large family
of programming languages. Scheme
-is the more clean and minimalistic dialect, and is what's mostly used in
+is the more clean and minimalist dialect of Lisp, and is what's mostly used in
academic circles.
Scheme itself has umpteen different "implementations", which share most of
their fundamentals, but have slightly different extensions and interact with
-the operating system differently. One major implementation used to be called
-PLT Scheme, and has just in the past few weeks changed their name to Racket.
-This is what we recommend you use. (If you're already using or comfortable with
-another Scheme implementation, though, there's no compelling reason to switch.)
+the operating system differently. One major implementation is called Racket,
+and that is what we recommend you use. If you're already using or comfortable with
+another Scheme implementation, though, there's no compelling reason to switch.
+
+ Racket stands to Scheme in something like the relation Firefox stands to HTML.
+
+ (Wikipedia on [Lisp](http://en.wikipedia.org/wiki/Lisp_%28programming_language%29),
+[Scheme](http://en.wikipedia.org/wiki/Scheme_%28programming_language%29),
+and [Racket](http://en.wikipedia.org/wiki/Racket_%28programming_language%29).)
- Racket stands to Scheme in something like the relation Firefox stands to HTML.
+* **Caml** is one of two major dialects of *ML*, which is another large
+family of programming languages. Caml has only one active "implementation",
+OCaml, developed by the INRIA academic group in France. Sometimes we may refer to Caml or ML
+more generally; but you can assume that what we're talking about always works more
+specifically in OCaml.
-* **Caml** is one of two major dialects of *ML*, which is another large
-family of programming languages. Caml has only one active implementation,
-OCaml, developed by the INRIA academic group in France.
+ (Wikipedia on [ML](http://en.wikipedia.org/wiki/ML_%28programming_language%29),
+[Caml](http://en.wikipedia.org/wiki/Caml),
+and [OCaml](http://en.wikipedia.org/wiki/OCaml).)
-* Those of you with some programming background may have encountered a third
+
+* Those of you with some programming background may have encountered a third
prominent functional programming language, **Haskell**. This is also used a
lot in the academic contexts we'll be working through. Its surface syntax
differs from Caml, and there are various important things one can do in
each of Haskell and Caml that one can't (or can't as easily) do in the
-other. But these languages also have a lot in common, and if you're
-familiar with one of them, it's not difficult to move between it and the
+other. But these languages also have *a lot* in common, and if you're
+familiar with one of them, it's generally not hard to move between it and the
other.
-[[How to get the programming languages running on your computer]]
-
-[[Family tree of functional programming languages]]
+ (Wikipedia on [Haskell](http://en.wikipedia.org/wiki/Haskell_%28programming_language%29).)
-## Recommended Books ##
+<a name=installing></a>
+[[How to get the programming languages running on your computer]]
-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.
-* *An Introduction to Lambda Calculi for Computer Scientists*, by Chris
-Hankin, currently $17 on
-[Amazon](http://www.amazon.com/Introduction-Lambda-Calculi-Computer-Scientists/dp/0954300653).
+## Recommended Books ##
-* (Another good book covering the same ground as the Hankin book, but
-more thoroughly, and in a more mathematical style, is *Lambda-Calculus and Combinators:
-an Introduction*, by J. Roger Hindley and Jonathan P. Seldin. If you choose to read
-both the Hankin book and this book, you'll notice the authors made some different
-terminological/notational choices. At first, this makes comprehension slightly slower,
-but in the long run it's helpful because it makes the arbitrariness of those choices more salient.)
+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.
+* *An Introduction to Lambda Calculi for Computer Scientists*, by Chris
+Hankin, currently $18 paperback on
+[Amazon](http://www.amazon.com/dp/0954300653).
* *The Little Schemer, Fourth Edition*, by Daniel P. Friedman and Matthias
-Felleisen, currently $23 on [Amazon](http://www.amazon.com/exec/obidos/ASIN/0262560992).
+Felleisen, currently $29 paperback on [Amazon](http://www.amazon.com/exec/obidos/ASIN/0262560992).
This is a classic text introducing the gentle art of programming, using the
functional programming language Scheme. Many people love this book, but it has
an unusual dialog format that is not to everybody's taste. **Of particular
a free sample chapter [at the MIT Press web page for the
book](http://www.ccs.neu.edu/home/matthias/BTLS/).
-* *The Seasoned Schemer*, also by Daniel P. Friedman and Matthias Felleisen, currently $28
-on [Amazon](http://www.amazon.com/Seasoned-Schemer-Daniel-P-Friedman/dp/026256100X)
+* *The Seasoned Schemer*, also by Daniel P. Friedman and Matthias Felleisen, currently $29 paperback
+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.
-* *The Little MLer*, by Matthias Felleisen and Daniel P. Friedman, currently $27
+* *The Little MLer*, by Matthias Felleisen and Daniel P. Friedman, currently $31 paperback / $29 kindle
on [Amazon](http://www.amazon.com/Little-MLer-Matthias-Felleisen/dp/026256114X).
-This covers some of the same introductory ground as The Little Schemer, but
-this time in ML. It uses another dialect of ML (called SML), instead of OCaml, but there are only
-superficial syntactic differences between these languages. [Here's a translation
-manual between them](http://www.mpi-sws.org/~rossberg/sml-vs-ocaml.html).
+This covers much of the same introductory ground as The Little Schemer, but
+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.
+([Here's a translation manual between them](http://www.mpi-sws.org/~rossberg/sml-vs-ocaml.html).)
+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.
+
+* Another good book covering the same ground as the Hankin book, but
+more thoroughly, and in a more mathematical style, is *Lambda-Calculus and Combinators:
+an Introduction*, by J. Roger Hindley and Jonathan P. Seldin, currently $74 hardback / $65 kindle on [Amazon](http://www.amazon.com/dp/0521898854).
+This book is substantial; and although 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.
+If you choose to read both the Hankin book and this book, you'll notice the authors made some different
+terminological/notational choices. At first, this makes comprehension slightly slower,
+but in the long run it's helpful because it makes the arbitrariness of those choices more salient.
+* 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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