+During the course, we'll be encouraging you to try out various things in Scheme
+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 'true), 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 (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 effect). Programming languages like C and Python and JavaScript and so on are all of this sort.
+
+In fact, nothing that gets marketed as a "programming language" is really completely 100% functional/declarative, and even the
+imperatival languages will have purely functional fragments (they evaluate `1+2` to 3, also). So these labels are really
+more about *styles* or *idioms* of programming, and 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. Even languages like Python and JavaScript are sometimes
+described as "more functional" than some other languages. The language C is about as non-functional as you can get.
+
+* **Scheme** is one of two 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
+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 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).)
+
+* **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.
+
+ (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
+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.
+
+ (Wikipedia on [Haskell](http://en.wikipedia.org/wiki/Haskell_%28programming_language%29).)
+
+
+<a name=installing></a>
+[[How to get the programming languages running on your computer]]
+
+<!--
+[[Family tree of functional programming languages]]
+
+[[Translating between OCaml Scheme and Haskell]]
+
+## What is Functional Programming? ##
+
+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.
+
+Read more about the [uptake of Haskell](http://steve-yegge.blogspot.com/2010/12/haskell-researchers-announce-discovery.html) among programmers in the street.
+-->
+
+## Recommended Books ##
+
+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 $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
+interest for this course** is the explanation of the Y combinator, available as
+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 $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 $31 paperback / $29 kindle
+on [Amazon](http://www.amazon.com/Little-MLer-Matthias-Felleisen/dp/026256114X).
+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 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.
+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.