## Notes

• If the instructions below seem overwhelming, note that it should be possible to do a lot of this course using only demonstration versions of these languages that run in your web browser.

• We were updating this page vigorously until about 2:30 pm on Saturday 31 January. Now it is relatively stable, but we'll tweak it as we learn more. We encourage you to try to get the software set up sooner rather than later, and those who do so first should let us know how things go---whether it's smoothly or not---so that we might possibly refine or expand the instructions for others. It'd be great if you took careful notes of what you did, step by step. If our instructions are broken or misleading or incomplete, and you figure out how to fix them on your own, it'd also be great if you can tell us what went wrong and exactly what you did to achieve joy.

• On a Mac or Linux system, you have a number of system directories such as /usr and /Library, and also your user home directory which will be named something like /User/george or /home/george if you are george. Other ways to refer to the user home directory are as ~ (the tilde character) or as $HOME. When installing software, you sometimes have a choice of whether to install it into the system directories or in subdirectories of your user home. When this choice was available, I made the instructions that follow select the latter. This makes it somewhat harder for things to get messed up, and makes it somewhat easier for you to remove things later. If you're using a Mac without MacPorts (explained below), then Chicken and OCaml will be installed under your user home; but Racket's and GHC's Installers put them into system directories. ## Identifying your system We'll assume you're using either Mac OS X, or Windows, or Linux. If you're running iOS, you'll have a much harder time (perhaps impossible, perhaps not) getting this software to run on your machine, and we can't give you any guidance. If you're using Mac OS X, take note of what version of the Mac OS you're running. (Under the Apple Menu, select "About this Mac".) • Leopard (10.5) • Snow Leopard (10.6) • Lion (10.7) • Mountain Lion (10.8) • Mavericks (10.9) • Yosemite (10.10) Furthermore, Mac users will be in one of two subgroups: • You'll have Apple's Xcode and the independent MacPorts system installed. (Probably you don't. If you don't know what I'm talking about, you don't have these.) If you don't have these, but want to try this route, you can read about the MacPorts system 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. (Though as it happens, MacPorts only has an older version of our chosen implementation of Scheme.) There are also other package management systems available for the Mac, notably Homebrew and Fink. I only know a little bit about them. There are instructions about how to get Xcode on the Installing MacPorts page. Some versions of Xcode are available for free on the Mac App Store. Other versions are available through Apple's Developer website (some of these are free, but do require you to register with Apple as an "Apple Developer", which involves clicking to accept a legal agreement with Apple). I have an older version of this installed. If you download a recent version, email me and let me know how the process works so I can tell others. • 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 sometimes those conditions aren't 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. (Most Windows users will be in this group.) You might in theory have a different group of compilers installed (MinGW, or 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. For everyone, a general item to take note of is what "processor architecture" your machine is running. Three of the possibilities are: • One of Intel's i386, i486, i586, i686 architectures. These are collectively known as "x86" or "IA-32" or sometimes just "32-bit". • Intel or AMD's x86_64 architecture. This is also called "x64" or "amd64" or "IA-64" or sometimes just "64-bit". (Note that these aren't "x86" machines, even though "x86_64" starts with those letters.) • ARM or some other architecture. These are generally lower-powered machines, like iPads. Some of the software we're proposing might in principle be capable of running on such machines, but installers don't seem to be available. We'll assume you have access to an x86 or x86_64 machine. On Linux or Mac OS X, you can open a terminal and type uname -m. If the result is "x86_64", then you've got x64/64-bit. If it's "i386" or something like that, then you've got x86/32-bit. I think that Mac OS Xs from 10.7 / Lion forward have all been x86_64-only. On Windows, here is a page that can help you figure this out. I think that most machines running Windows XP will be x86/32-bit (unless it's a version of Windows with "64-bit" or "x64" in its title); machines running Windows Vista or Windows 7 or Windows 8 could be running either x86/32-bit or x64/64-bit. ## 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. ## Preliminaries If you're using Linux or a Mac without MacPorts, then open a Terminal and type the following. You probably want to copy and paste it to make sure you don't make mistakes: (IFS=:; for p in$PATH; do [ /usr/local/bin = "$p" ] && exit 0; done; echo 'export PATH="/usr/local/bin:$PATH"' >> ~/.bash_profile)
mkdir -p ~/bin
echo 'export PATH="$HOME/bin:$PATH"' >> ~/.bash_profile


## Getting Scheme

Scheme is one of two or three major dialects of Lisp, which is a large family of programming languages. The other dialects are called "Common Lisp" and "Clojure". Scheme is the more clean and minimalist 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. (A few years back they were called PLT Scheme, but then they changed their name to Racket.) If you're already using or comfortable with another Scheme implementation, though, there's no compelling reason to switch.

Another good Scheme implementation is Chicken. For our purposes, this is in some respects superior to Racket, and in other respects inferior. If you have any issues with installing or using Racket, you could try this out instead. You might even want to install both.

Racket and Chicken stand to Scheme in something like the relation Firefox stands to HTML. They are two programs (or platforms) among others for working with the Scheme language; and many of those programs (or web browsers) permit different extensions, have small variations, and so on.

Racket has several components. The two most visible components for us are a command-line interpreter named "racket" and a teaching-friendly editor/front-end named "DrRacket". You will probably be working primarily or wholly in the latter.

The current version of Racket is 6.1.1 (released November 2014).

• To install in Windows

Go to http://racket-lang.org/download/. Download and install the "Windows x64" version. (Or the "Windows x86" verson if you have an older, 32-bit system.)

• To install on Mac without MacPorts

Go to http://racket-lang.org/download/. Download and install the option for your system, most likely "Macintosh OS X (Intel 64-bit)".

After you copy the files from the Installation disk to your /Applications folder, I think it's helpful to do these additional steps. In a Terminal, type:

sudo ln -s /Applications/Racket*/DrRacket.app /Applications/
ln -s /Applications/Racket*/bin/racket ~/bin/


(If you get an error about ".../bin/: No such file or directory", then you didn't follow the Preliminary instructions above.)

Then you can launch Racket either by double-clicking the DrRacket icon in your Applications folder (this gives you the GUI interface); or by typing racket in a Terminal (this gives you the command-line version).

Instead of, or in addition to, the first line above, you could drag the DrRacket.app icon to your Dock.

• To instead install Chicken Scheme on Mac without MacPorts

Here are the exact steps I just verified worked. Note that I first installed the Haskell Platform, described further down this page; that installed some developer tools that were needed to build and install Chicken. If you don't know how to open a Terminal, move between directories, copy / rename / delete files and so on, then you're probably best off not doing this. You could break something.

1. Go to http://code.call-cc.org, and click the "Source code" link near the top. Current version is 4.9.0.1, released November 2014. This should fetch a file to your download folder, and will probably automatically unpack that file into a folder, "chicken-4.9.0.1". Click on that folder and press command-C / Copy, then open a Terminal.
2. In the terminal type cd followed by a space, then press command-V / Paste. Then press enter. This will move your session into the folder you just downloaded.
3. Type make PLATFORM=macosx XCODE_DEVELOPER= XCODE_TOOL_PATH=/usr/bin PREFIX=$HOME The options starting with XCODE_ are to tell the Chicken build scripts that I've got the developer tools installed in my main system, rather than as part of Xcode. (That's where the Haskell Platform installer put them.) Continuing: 1. Wait a while while Chicken builds. 2. If it finishes with no errors, then type make PLATFORM=macosx XCODE_TOOL_PATH=/usr/bin PREFIX=$HOME install. This will install Chicken in your user home directory.
3. At this point you can type which chicken. It should give you an answer of "/Users/yourname/bin/chicken".
4. In your terminal, type chicken-install r7rs datatype matchable monad. This will download, build, and install a few extensions (Chicken calls them "eggs") relevant to ideas we'll be working with in this course.
• To install on Mac with MacPorts

Unfortunately, MacPorts doesn't have Racket itself available. It only has an older version from when they still called themselves PLT Scheme. And even then, it only has the command-line program "mzscheme" (what's nowadays called "racket"); it doesn't have the GUI program that corresponds to what's now called "DrRacket". You can install mzscheme by opening a Terminal window 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. Or you could try the Chicken Scheme implementation instead of Racket. This is more current. To do that, type:

sudo port install chicken readline


Whether you use mzscheme or Chicken, I recommend also typing:

sudo port install rlwrap


then if you ever use the command-line program mzscheme (or racket, for that matter), you should start it by typing rlwrap mzscheme (or whatever). 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 racket


It's very likely that your packaging system has some version of 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 and Debian 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 (or whatever). 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. 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.

It's helpful if in addition to OCaml you also install the Findlib add-on and/or the OPAM "package manager." These will make it easier to install additional add-ons further down the road. However, if you're not able to get them working, don't worry about it much.

The current version of OCaml is 4.02.1 (released October 2014).

• In your web browser:

There is a (slow, bare-bones) version of OCaml available for online use at http://try.ocamlpro.com/.

• To install in Windows

There are five different strategies for installing OCaml on Windows. I don't know which works best.

1. First, you can 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 an earlier version of OCaml (4.01.0, from September 2013) is available.

2. A second strategy uses a package called OCPWIN. This also installs only version 4.01.0.

3. The three remaining strategies in some way use the Cygwin environment, mentioned earlier on this page. At least one of those three methods will automatically fetch and help you install Cygwin. The first method listed on that page says it installs version 4.00.1, but really it's been updated and now installs the (somewhat newer, but still not the newest) version 4.01.0.

Some of these methods may automatically install Findlib for you. If not, you can try installing it yourself but I think you'll need the Cygwin system installed to do so. I'm not going 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

The people in charge of OCaml (they're at the French research institute INRIA) have stopped making pre-built packages for Mac OS X. One option you have is to use their package for a slightly older version of OCaml, 4.01.1 from Sept. 2013. You can find that as a "Precompiled binary for Mac OS X" on this page. If, when you attempt to install this package, you get an error about its being from an "unidentified developer," you need to control-click on the ocaml.pkg file and select "Open", then when the warning box appears again, this time there will be an "Open" button that you can click. Then you can continue running the Installer.

A second option is to install the OPAM package manager and use that to build and install the latest version of OCaml. Here's how to do that:

1. Download this file and note where it gets saved to. If it opens in your browser, then type command-S / Save Page and save it somewhere on your disk, again noting its location.

2. Open a terminal and type:

sh /path/to/opam_installer.sh ~/bin


Except replace /path/to with the real location, that you noted in step 1. When prompted "Do you want OPAM to modify ~/.bash_profile and ~/.ocamlinit?", say "y".

3. If that works, then type:

opam init --comp 4.01.0


or whatever it was that the OPAM installer prompted you to type. This will download and install a fresh version of OCaml, and will take a bit of time.

• To install on Mac with MacPorts

You can install the current version of OCaml (4.02.1, from October 2014), together with the Findlib add-on and OPAM package manager, by opening a Terminal and typing:

sudo port install ocaml ocaml-findlib opam


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.

• To install on Linux

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

sudo apt-get install ocaml opam camlp4-extra ocaml-findlib


That will install a version of OCaml and the Findlib add-on and OPAM package manager.

If you're using Ubuntu "Utopic" (14.10), there's a note on the OPAM home page warning that its version of OPAM is broken, and not to use it. Here's how you can get (OCaml and) OPAM from a newer repository:

sudo apt-get install -y software-properties-common
sudo add-apt-repository -y ppa:avsm/ppa
sudo apt-get update
sudo apt-get install ocaml opam


If for some reason you can't get OCaml through your Linux 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-1.5.5.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.

## Getting Haskell

This last installation is less crucial than the others, since we will be focusing primarily on Scheme and OCaml. However we, and the readings you come across, will sometimes mention Haskell, so it might be worth your installing this too, so that you have it available to play around with.

Haskell is used a lot in the academic contexts we'll be working through. At one point, Scheme dominated these discussions but now Haskell seems to do that.

Haskell's 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 generally not hard to move between it and the other.

• In your web browser:

There is a (slow, bare-bones) version of Haskell available for online use at http://tryhaskell.org/.

Like Scheme, Haskell has a couple of different implementations. The dominant one, and the one we recommend you install, is called GHC, short for "Glasgow Haskell Compiler". To install this on your machine, there are a couple of different strategies. It's helpful to understand some lingo as you begin this process:

• As mentioned, GHC is the main Haskell engine or compiler you'll be installing. The current version is 7.8.4, from December 2014.
• gcc and llvm/clang and Xcode and MinGW are names for other compilers on various systems. Oftentimes these will be used during the installation process to get GHC up and running. Some of the strategies described below will help you install these if they're not already on your machine.
• alex and happy and haddock are names of various Haskell helper programs that GHC uses to get up and running.
• cabal is a "package manager" for Haskell. It allows you to install libraries or extensions that other people have built. (Usually those are published at the Hackage Package Database.) Some of these are experimental and may not always work; others are quite fundamental and are almost de facto parts of what people expect in a Haskell system.
• The Haskell Platform is a standard bundle that includes a specific version of GHC, plus specific versions of some of the most popular libraries or extensions. This is updated once or twice a year. The current version is 2014.2.0.0, from August 2014. It includes GHC version 7.8.3.

The easiest way to get up and running with Haskell/GHC is to install the Haskell Platform. Here's how to do that on Windows:

On Mac without MacPorts:

• Go to https://www.haskell.org/platform/mac.html and follow the instructions. This requires Mac OS X 10.6 / Snow Leopard or later; but there is a link to an earlier version of the Haskell Platform, that's built for Mac OS X 10.5 / Leopard. During the installation, you may be prompted to install "the command line developer tools"; this is a portion of what Apple bundles together with Xcode (mentioned above on this page). The installer will take care of getting these for you if you give it permission.

On Mac with MacPorts:

• In a Terminal, type sudo port install haskell-platform.

On Ubuntu or Debian Linux:

• In a Terminal, type sudo apt-get install haskell-platform.

If any of the instructions above don't work, then you can try alternative instructions for Mac or Windows or Ubuntu. Note that this method doesn't install all the extensions that are part of the Haskell Platform, but only the core pieces of GHC. You can use Cabal to download and manage any extra extensions you turn out to need, down the road.

After installing Haskell, open a Terminal and type:

cabal update


It may give you a message about updating your PATH variable. On my Mac, I was prompted to do this:

echo 'export PATH="$HOME/Library/Haskell/bin:$PATH"' >> ~/.bash_profile


On a Linux machine, or if you installed Haskell differently on your Mac, you might have to type instead:

echo 'export PATH="$HOME/.cabal/bin:$PATH"' >> ~/.bash_profile


Some instructions may say to use .bashrc instead of .bash_profile. These files do similar jobs.

After issuing the relevant echo command, I exited the Terminal and started a new Terminal session. Now if I type echo \$PATH I should see the directory I just added in the list. Now I can contine setting up Cabal. I type:

which alex happy


If that gives me back two pathnames, one to the program alex and the other to the program happy, then I'm already finished. If not, then I type:

cabal install alex happy


This installs those two programs. They are helpers that Cabal needs to build and install some packages.