We'll assume you're using either Mac OS X, or Windows, or Linux.

If you're using Mac OS X, take note of what version of the Mac OS you're running: "Tiger" 10.4, or "Leopard" 10.5, or "Snow Leopard" 10.6. Furthermore, you'll be in one of two subgroups:

• You'll have Apple's Xcode and the independent MacPorts system installed.

Xcode is available at http://developer.apple.com/technologies/tools/xcode.html. You have to register as an Apple Developer to download it. This is free but requires you to accept a legal agreement with Apple. The latest version of Xcode to work with Leopard is 3.14; more recent versions require Snow Leopard.

The MacPorts system is available at http://www.macports.org/. This automates the building of Unix-type software on your Mac; it makes it a lot easier to check for dependencies, use more-recent versions of things, and so on.

• Or you won't have those installed. (Most Mac users will be in this group.) Then you'll need pre-packaged (and usually pretty GUI) installers for everything. These are great when they're available and kept up-to-date; however those conditions aren't always met.

If you're using Windows, you'll be in one of two subgroups:

• You'll have the Cygwin system http://www.cygwin.com/ installed. This puts a Unix-like layer on top of your Windows system, and makes it easier for you to use the same software everybody else will be using, without its needing as much special-for-Windows treatment. However, many of you won't have this installed.

• You won't have Cygwin installed. You might in theory have a different group of compilers installed (Microsoft Visual C++) but we'll assume that the overwhelming majority of users in this group don't have access to a compiler and need pre-packaged installers for everything.

If you're using Linux, you could be using any one of numerous packaging systems.

• We'll give examples using the packaging system shared by Debian and Ubuntu, and we'll assume that those of you using different packaging systems will know how to make the relevant substitutions. You may also want to take note of the output of the "uname -srm" command. On my machine this tells me "Linux 2.6.35-ARCH x86_64". That tells me I'm running the x86_64 (as opposed to the i686 or i386 or whatever) version of Linux, and that I'm running kernel version 2.6.35.

## PLEASE REPORT PROBLEMS (AND SOLUTIONS!)

We haven't tested these instructions ourselves, and they're not explicit step-by-step instructions in any case. If you encounter troubles, please email to let us know so that we can amend the instructions to help others. If you figure out how to fix the problem youself (and please do), please also write with suggestions how we can change these instructions to make the process easier and more straightforward for others.

## Getting Scheme

Scheme is one of two major dialects of Lisp, which is a large family of programming languages. The other dialect is called "Common Lisp." 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 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.)

Since the name change is so recent, you're likely to run across both sets of names.

PLT/Racket stands to Scheme in something like the relation Firefox stands to HTML. It's one program among others for working with the language; and many of those programs (or web browsers) permit different extensions, have small variations, and so on.

PLT Scheme had several components. The two most visible components for us were the command-line interpreter "mzscheme" and a teaching-friendly editor/front-end "DrScheme". In Racket these have been renamed "racket" and "DrRacket", respectively.

There is a (slow, bare-bones) version of Scheme available for online use at http://tryscheme.sourceforge.net/.

• To install in Windows

• To install on Mac without MacPorts

• To install on Mac with MacPorts

You can install a command-line version of PLT Scheme (dating from early 2009) by opening a Terminal and typing:

 sudo port install mzscheme


If you want the GUI components, I think you'll need to use the "Mac/without MacPorts" installation options above.

I recommend also typing:

sudo port install rlwrap


then if you ever use the command-line program mzscheme (or racket), you should start it by typing rlwrap mzscheme. This gives you a nice history of the commands you've already typed, which you can scroll up and down in with your keyboard arrows.

• To install on Linux

Use your packaging system, for example, open a Terminal and type:

 sudo apt-get install plt-scheme


It's very likely that your packaging system has some version of PLT Scheme (or Racket) available, so look for it. However, if you can't find it you can also install a pre-packaged binary from the Racket website at http://racket-lang.org/download/. Choose the option for your version of Linux (Ubuntu, Debian, and two varieties of Fedora are available).

As above, I recommend you also type:

sudo apt-get rlwrap


then if you ever use the command-line program mzscheme (or racket), you should start it by typing rlwrap mzscheme. This gives you a nice history of the commands you've already typed, which you can scroll up and down in with your keyboard arrows.

## Getting OCaml

Caml is one of two major dialects of ML, which is another large family of programming languages. The other dialect is called "SML" and has several implementations. But Caml has only one active implementation, OCaml or Objective Caml, developed by the INRIA academic group in France.

It's helpful if in addition to OCaml you also install the Findlib add-on. This will make it easier to install additional add-ons further down the road. However, if you're not able to get that working, don't worry about it much.

• To install in Windows

Go to http://caml.inria.fr/download.en.html. You can probably download and install the "Self installer for the port based on the MinGW toolchain" even if you don't know what MinGW or Cygwin are. Some features of this require Cygwin, but it looks like it should mostly work even for users without Cygwin. At the time of this writing, only an installer for the previous version of OCaml (3.11.0, from January 2010) is available.

To install the Findlib add-on, you must have the Cygwin system installed. We assume few of you do, so we're not going to try to explain how to do this. If you want to figure it out yourself, go to the Findlib website at http://projects.camlcity.org/projects/findlib.html.

• To install on Mac without MacPorts

To install the Findlib add-on, you'll need the Xcode development tools to compile it yourself. Once you get that far, it's probably easiest for you to install MacPorts and just install things using the MacPorts instructions. (Use the MacPorts version of OCaml, instead of installing the package from the caml.inria.fr website, as described above) However, if you do have Xcode, and want to do without MacPorts, then what you need to do is download Findlib from http://download.camlcity.org/download/findlib-1.2.6.tar.gz. Unpack the download, open a Terminal and go into the folder you just unpacked, and type:

./configure
make package-macosx


This will build an installer package which you should be able to double-click and install.

• To install on Mac with MacPorts

You can install the previous version of OCaml (3.11.2, from January 2010), together with the Findlib add-on, by opening a Terminal and typing:

sudo port install ocaml caml-findlib


As with Scheme, it's helpful to also have rlwrap installed, and to start OCaml as rlwrap ocaml. This gives you a nice history of the commands you've already typed, which you can scroll up and down in with your keyboard arrows.

• More details about installing OCaml on Macs, if needed

• To install on Linux

Use your packaging system, for example, open a Terminal and type:

sudo apt-get install ocaml ocaml-findlib


That will install a version of OCaml (probably 3.11.2, from January 2010) and the Findlib add-on.

If for some reason you can't get OCaml through your packaging system, you can go to http://caml.inria.fr/download.en.html. Pre-packaged binary installers are available for several Linux systems.

If you can't get findlib through your packaging system, you'll need to download it from http://download.camlcity.org/download/findlib-1.2.6.tar.gz. and use gcc to compile it yourself. If you don't know how to do that, you probably don't want to attempt this. Here are the INSTALL notes: https://godirepo.camlcity.org/svn/lib-findlib/trunk/INSTALL.

As with Scheme, it's helpful to also have rlwrap installed, and to start OCaml as rlwrap ocaml. This gives you a nice history of the commands you've already typed, which you can scroll up and down in with your keyboard arrows.