Teaching Programming Languages with Scala

This semester, I am teaching the undergraduate programming languages course at SJSU, a required course for CS majors. The course has two objectives:

• To give students significant exposure to a programming paradigm other than OO
• To make students understand the process of translating a high-level language into machine (or VM) code

The canonical way to meet these objectives is to teach Scheme, and to build simple interpreters and compilers. It is not the most popular course. Most of our students just don't think Scheme is all that cool. When I want them to admire the elegance of closures and continuations, they are still hung up over parentheses and let.

This semester, I am trying something new. I am using Scala as my functional language. The syntax is accessible to the students (they all know Java), and they see Scala mentioned on dzone.com, so it isn't just something of interest to a bunch of pointy-headed professors.

In the first few weeks, I am restricting myself to the functional subset of the language:

• val, not var
• No while, just recursion
• Immutable lists, just with head, tail, and ::
• The higher-order functions in the List class: map, filter, /:, etc.

I can do exactly the same as in Scheme, except without the parentheses. Does it work? I had a few lectures, and here are my initial observations.

• Students need to install the JDK and Scala on their laptops. The worst part was setting up Java on Windows. If the installer must put the JDK into Program Files, couldn't it at least add the bin directory to the PATH? It requires superhuman effort to get the less talented students to edit the system configuration or to deal with spaces in file names in the command shell.
• The DOS shell still sucks eggs, just as it has ever since I first saw it in Windows 3.0. The better students run Linux, Mac OS, or Cygwin with rxvt. Microsoft sends a powerful signal to budding computer scientists. That signal is: "We don't give a !@#$ about you!".
• The Scala interpreter is great. Students enjoy the immediate feedback.
• The biggest hangup so far has been the strong typing, somewhat to my surprise. x : Int instead of int x, but one quickly gets used to that. However, typing

  append(lst : List[Any], a : Any) : List[Any]

  into an interpreter window is no great joy. I expect this will get better when we move to Eclipse, where the IDE can take advantage of the strong typing.

Interested in following along? Click on the links of this schedule. There are lab assignments in each lecture. If you need a hint with one of the labs, leave a blog comment.