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PL: Resources

Class Notes

These are the class notes files. In some places they are in pretty raw form, intended mainly for reference, code examples etc. They are not a substitute for taking notes in class, and they certainly cannot compensate for not coming in. Also, they are not guaranteed to cover all of the material that was presented in class.

Handouts

• Email and Piazza Group Policies: Guidelines for writing posts (in piazza group posts and in general).
• Style Guide: A collection of guidelines for writing better code.
• Tips: Some useful tips for PL work, DrRacket tips and more.
• Racket Evaluation Rules: Formal rules for evaluating Racket Using substitution.
• Exam Format: What are the exam options in this course?

Interpreters

• ae.rkt — The AE interpreter
• wae.rkt — The WAE interpreter
• flang.rkt — The Flang interpreter
• flang-env.rkt — The Flang interpreter, using environments
• church.rkt — Making Schlac into a practical language (not an interpreter)
• church-alternative.rkt — An alternative "Church" encoding: use lists to encode numbers
• toy.rkt — The TOY interpreter
• sloth.rkt — The SLOTH interpreter
• sloth-cached.rkt — A call-by-need version of the SLOTH interpreter
• picky1.rkt — The Picky interpreter, verbose version
• picky2.rkt — The Picky interpreter, almost no explicit types
• picky3.rkt — The Picky interpreter, no explicit types
• simple-web-language.rkt — Simulation of web interactions with a CPS converter (not an
• cps-language.rkt — A language that is CPS-transformed (not an interpreter)
• continuation-based-web-library.rkt — Simulation of web interactions with Racket’s built-in continuation
• amb.rkt — The ambiguous operator and related utilities.
• producer.rkt — An implementation producer functions

Software

We will use the Racket environment extensively. DrRacket, the major component of Racket, will be used to develop code, debug, and submit homeworks. CCS computers have an updated version installed (available on both Unix and Windows). To use it on your own machine, get it from the Racket website. Binary installers exist for all major operating systems, and the course work will be platform independent.

Racket has a system for distributing software bundles that will be used to get a course-specific plugin. This packages both specific functionality for each homework, and an integrated tool for homework submissions. Once you have Racket installed, download the plugin package, and use the “Setup PLT” application to install it. You can also use “Install .plt File” in the File menu, and enter the URL for the plugin.

Note: The handin server uses a dedicated port for communication. You need to work from a network that does not restrict this port — for example, if you use Northeastern’s ‘NUwave-guest’ network, then you will not be able to connect to the server. ‘NUwave’ (which requires you to authenticate through myNEU) does not have this restriction.

To set-up your account:

• Restart DrRacket (you should see a NEU icon on startup, and a “PL Handin” in DrRacket’s toolbar).
• Menu: File > Manage PL Handin Account... (Your computer will establish a secure connection to the handin server at this point.)
• Make sure the “New User” tab is selected, and fill in the form:
  • ‘Username’ should be a lowercase alphanumeric string
  • ‘Full Name’ should be your full name (as you want to be known in class, not necessarily your ‘formal’ name: “Bob Smith” is better than “Robert William Junior of the New England Smiths”).
  • ‘Email’ should be your active email — this address will be used to contact you, so make sure you enter the email address you use most frequently (for example, enter your Gmail address if you use Gmail every day, even if you have a @ccs.neu.edu address).
  • ‘ID#’ is the last 4 digits of your NEU ID.
  • Enter a password, twice. (Make sure you remember your password.)
• Click the “Add User” button — if everything went fine, you should see a “Success” message at the top of the dialog.
• If you had a mistake in the information for your account, open up the “Manage...” dialog, and choose the “Change Info” tab; enter your password in the “Old Password” field and re-fill any fields you want to change and/or a new password. (Once you fill your current password you can click the “Get Current Info” button to retrieve the current values.) If you forgot your password, mail us and we will re-set it.
• To submit a file, open it in DrRacket, and hit the “PL Handin” button, choose the homework you’re submitting to, enter your password and hit the big Handin button.
• To verify the file you sent, you can click the “PL Handin” button, choose the homework, check the “Retrieve” checkbox, enter your password and click the big button. You can even use this method if you want to work on different machines: retrieve your file, edit, and submit to save.
• Each time DrRacket starts, the plugin will check for updates, and will ask you if it found that a newer version is available.
  The plugin will be updated frequently, follow the web page and the piazza group (see below) for announcements.

Additional software may be used later in the course.

Piazza Group

There is a piazza group for this course at Piazza.com. The piazza group is the main medium for discussions, questions, announcements etc. You should use it if you have any questions, so others can benefit from the discussion as well. If you want to ask a question that involves showing your solution code, make sure that you choose the “private” option. Do not to post any homework code on the piazza group without using the “private” option. Direct emails to the course staff should be your last resort. Consult the Email and Piazza Group Policies handout for further details about piazza group posts and emails.

Note that you do not need to request to be subscribed to the mailing list — you will get added after you register with the submission server.

IRC

IRC, or “Internet Relay Chat” is a text-based chat protocol where people can join channels on IRC servers and communicate. IRC is sometimes refered to as “interactive notepad”. The major benefit of using IRC is real-time conversations with fellow class members as well as course staff.

If you have a CCIS account, you are almost ready to start using IRC. The following will describe a basic configuration, as described by jmendel (aka John Mendelewski). Feel free to set up your client as you wish.

• Choose your favorite CCIS Linux machine.
• SSH into this machine. Many Linux distributions have OpenSSH installed by default, so just type

  ssh ⟨CCIS-username⟩@⟨machine⟩.ccs.neu.edu

  Note that login is the preferred machine for such things (specifically, it’s a machine that cannot be rebooted by random students).
  If you are using Windows or Mac, please look into a SSH client for that OS. For Windows, putty is a popular free ssh client that works well. Mac OS X comes with an ssh command that you can run in the Terminal.
• Once presented with a prompt, similar to [⟨username⟩@⟨machine⟩] ~ % use the command

  screen

  The screen command allows you to run programs that will live on this machine even after you log off — think of it as a kind of a virtual text session manager. This is useful, since it makes it possible to continuously run the IRC client so that you can reconnect to it and see everything that was said while you were away.
  Important: You should use screen with no arguments only once since this will create a new session. Later you will use screen -rd to reconnect to an existing session.
• The screen should flash, possibly displaying a welcome message. Press enter until you are given a prompt again. From here,execute the command

  irssi

  This is a console based IRC client. This is good because you can run it from screen, and as said, keep the program running even after you leave.
• To connect to the CCIS IRC server (called “irc”), type in the irssi prompt:

  /connect irc

  Text should scroll down the screen now.
• Once it stops, you should identify yourself with the server. First, if you haven’t already, register by entering:

  /msg nickserv register ⟨some-password⟩

  This will secure the nickname you chose to you, and only you.
  If you’re registered, then you need to identify yourself using your password:

  /msg nickserv identify ⟨some-password⟩

  Please read up on google about how to use irssi. Here’s a link that seems useful.
  (Note: while doing the above, a number may show up at the bottom of your window. This means there is activity in a window that is not currently shown. To show this window, press Esc and that number.)
• Once you are identified, join the PL channels:

  /join #pl /join #pl-talk

  #pl-talk is the student-only channel (no instructor here), and #pl is the main course channel and Eli is usually there too. The content you post to these channels is up to you, but should follow the common guidelines of the mailing list.
• Now that you are running irssi inside screen, press Ctrl-A and then Ctrl-D (or just D). This will be caught by screen and make it “detach” your session. This means everything you are doing goes into a background process, waiting for you you to return. You should be back at the original prompt that you started with when you first connected into ⟨machine⟩. Feel free to log out of this machine with Ctrl-D or by typing exit.
• To get back to IRC later, ssh back into ⟨machine⟩ and issue the following command:

  screen -rd

  You should be back where you left off, with irssi still running. Repeat the Ctrl-A Ctrl-D to detach again.

Finally, IRC is a valuable resource: don’t abuse it! Specifically, you should not post any source code, and you should try to read homework texts thoroughly before you ask questions. This applies for both channels.

On-line books and other materials

There are lots of Racket and Scheme books on-line, a few good ones are:

• How to Design Programs: A good introductory book that uses Racket. We use this book in the introductory part of the course. (You should be familiar with it.) There is also a draft for a second edition of the book, How to Design Programs, second edition.
• Programming Languages: Application and Interpretation: This is the main textbook that we use. (See also the book website.)
• Structure and Interpretation of Computer Programs: A book written for a course at MIT, which has made the language popular early on. Widely known as the “Wizard Book”. It’s fun to go over it though it shows its age in several places.
• The Scheme Programming Language, 3rd ed: Another advanced book, and a version using the newer R⁶RS standard: The Scheme Programming Language, 4th ed.
• Racket Documentation: The Racket manuals have guides that introduce the language and demonstrate real-world uses. Specifically, see the More guide for a quick tutorial that gets you to implement a web server from scratch.
• Teach Yourself Racket is a quick crash course that will introduce you to Racket programming.

• Introduction to Programming Languages is a course at Brown, taught by Shriram Krishnamurthi who is the author of PLAI, with on-line videos of the lectures.
• Introduction to Systematic Program Design is an HtDP2e-based course, taught by Gregor Kiczales who is a very known lisper/schemer/racketeer.