Noulakaz

The blog of Avinash, Christina, Anya and Kyan Meetoo.

Education

Urgently looking for a project assistant

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Christina and myself have embarked on a consultancy project which will last for about 6 weeks. We urgently need a project assistant to assist us in doing some surveys in some schools and colleges and to analyze the results obtained.

That person should preferably be a proactive and autonomous student of the University (we don’t really care about the year) who wants to earn some money. He/she will have to travel to the schools and colleges and will therefore have to be (more or less) free at least two days per week.

Contact us directly if you are keen:

We need to find someone by Friday so hurry up!

Learning Scheme with me

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As you all know by now, I am currently teaching the Scheme programming language to my 2nd year students as a means to master the functional programming paradigm.

I started four weeks ago with a general introduction on programming paradigms and on the necessity to at least know the most important ones in order to become a decent programmer. As my students had already studied imperative and object-oriented programming become coming to my class, I offered them to teach functional programming (using Scheme), logic programming (using Prolog in principle) and scripting (using Ruby). This first lecture can be downloaded here.

The following week, I introduced Scheme by putting a lot of accent on the evaluation of expression and the definition of simple (mathematical functions). The lecture, which is available here, was followed by a lab sheet where the students were introduced to DrScheme and were asked to write a number of simple functions (like fahrenheit->celcius).

The next lecture was on recursion and I focussed on a number of mathematical functions like factorial, fibonacci, square root using Newton’s successive approximation etc. I spent some time introducing the concept of tail-recursion to them as well as the tail-recursion optimization that Scheme has to do.

As an example, this:

(define (o+ n m)
  (cond ((zero? m) n)
        (else (o+ (add1 n) (sub1 m)))))

runs in constant space (i.e. there are no recursive function calls at runtime) even though it is expressed recursively. During the lab, the students implemented and traced a number of recursive functions (using the tracing facilities found in MzScheme). They implemented o+’s friends, o-, o*, o/, o^, o=, o< and o> (corresponding, of course, to our usual +, -, *, /, ^, =, < and >) using tail-recursion so that they run as quickly as possible.

The last lecture which I had last Friday was on pairs and lists, the most fundamental compound data structures found in Scheme. I introduced them to car and cdr and showed them a number of fundamental algorithms acting on lists (like length). During the lab, I asked the students to implement a simple database of students and marks and this is inspired by what I read in Practical Common Lisp.

My observations

My lectures have been cool up to now. The students are lively and responsive to my jokes and “parentheses”. The labs also are going on nicely with students who are really learning new things and having fun in the process.

It’s too early to say whether they’ll become better programmers eventually but I feel they are on the right track…

Learning by experimenting (with Scheme)

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In his beautiful essay, The Art of Lisp & Writing, Richard Gabriel makes a strong case for the use of programming mediums instead of programming languages when either introducing programming to students or starting a new project.

He says:

“The difference between Lisp and Java, as Paul Graham has pointed out, is that Lisp is for working with computational ideas and expression, whereas Java is for expressing completed programs. As James [Gosling] says, Java requires you to pin down decisions early on. And once pinned down, the system which is the set of type declarations, the compiler, and the runtime system make it as hard as it can for you to change those assumptions, on the assumption that all such changes are mistakes you’re inadvertently making.


There are, of course, many situations when making change more difficult is the best thing to do: Once a program is perfected, for example, or when it is put into light-maintenance mode. But when we are exploring what to create given a trigger or other impetus—when we are in flow—we need to change things frequently, even while we want the system to be robust in the face of such changes. In fact, most design problems we face in creating software can be resolved only through experimentation with a partially running system. Engineering is and always has been fundamentally such an enterprise, no matter how much we would like it to be more like science than like art.”

[Highlights mine]

I too believe that learning and experimenting require a Language like Lisp, Scheme, Smalltalk, Python and Ruby which offer a read-eval-print-loop (i.e. an interactive shell). Naturally, you’ll always need the big-iron compilers but only when the program is perfected…

As Frederick Brooks writes in The Mythical Man-Month, plan to throw one away, you will anyhow…. In most engineering fields, prototypes are routinely built using more malleable materials than the ones that are going to be used in production (for e.g. airplane prototypes made of wood). It’s only in our field, Programming, that people build prototypes using production-quality (but extremely rigid and constraining) languages like C++ and Java and spend so much time and money in this process that they are forced to ship the prototypes to customers with obvious consequences!

Using a malleable programming language

This semester, I am going to teach Programming Languages to second year university students. Those students have been exposed to C++ in the first year and Java at the beginning of the second year. Both programming languages are good for expressing perfected programs but are bad for experimenting.

(By coincidence, there were two interesting discussions on Slashdot (One Two.) following an article by some professors criticizing Java. Joel Spolsky thinks that it is perilous to use Java at school. I won’t even mention C++ as I personally think it’s the worst (by far) language to be used for teaching programming!

Together with Pascal Grosset who will be handling one of the lab sessions, I have been thinking a lot about what paradigms (and, hence, what programming languages) to use for my lecture. I think that I’ll only have time to introduce three paradigms and, hence, at most three programming languages (or mediums).

This is what we have come up with:

  • Functional programming with Scheme
  • Logic programming with Prolog (or, maybe, Kanren)
  • Scripting with Ruby

The first lecture

I did my first Programming Languages lecture last Friday and I enjoyed it a lot. I arrived in the lecture theatre at around 9:00 and I quickly installed OpenOffice.org on the Windows laptop there as I had prepared my presentation using OO Impress.

During the installation, I asked the 180 students how many of them found programming easy and only a few raised their hands (remember – those are second year students). I was a little surprised because I thought there were more. Anyway, I told them about my little theory that they should make a lot of effort now to acquire knowledge to be effective when they work so that they can return home early and enjoy life instead of having to stay overtime everyday :-)

I also told them that we were going to focus a lot on the functional, logic and scripting paradigms. And I also tried to make them understand that becoming a competent programmer require practice like all artistic endeavors. My first real lecture on Scheme will only begin next Friday as tomorrow is a public holiday.

Why Scheme?

I have been a fan of the Scheme programming language since I was introduced to it during my first year as a university student in France. Since then I’ve found out that Scheme is used at top universities like MIT and Berkeley to teach programming. Why is that so? Because Scheme is easy to learn yet, easy to use yet powerful!

I have decided to use the fantastic DrScheme IDE. It is multi-platform (Linux, Mac OS X and Windows) and is a joy to use. It’s, naturally, open source software. I am currently in the process of installing DrScheme in all the Computer Science labs.

I am still wondering what textbook I’ll use… I bought “How to Design Programs” by Matthias Felleisen, Robert Bruce Findler, Matthew Flatt, Shriram Krishnamurthi a year ago and it is an excellent book written by some of the makers of DrScheme. I am a little bit hesitant to use it as it uses slightly customized versions of Scheme instead of the standardized Scheme. Anyway, I’m still making my mind.

I have also ordered the Schemer triumvirate through Amazon and I expect to receive them in one or two weeks.

“The Little Schemer” is a little book (how surprising!) that covers functions (closures) and recursion. Many of you may feel that recursion is simple but Scheme guarantees that tail-recursive functions are executed without using increasing stack space hence the book goes into a lot of detail.

The second book, “The Seasoned Schemer”, talks about mutable state (i.e. variables) and about the special control flow constructs based on the continuations found in Scheme. Continuations allow for coroutines, concurrency, etc. and are important to understand if one really wants to be a Schemer (a Scheme programmer).

The final book is “The Reasoned Schemer” which is a book on reasoning (aha!). It introduces Kanren, a small library to transform Scheme into a better-than-Prolog programming language for logic and inference.

Why not Lisp?

I’ve also ordered “Practical Common Lisp” by Peter Siebel from Amazon. I have decided not to use Lisp because the de-facto IDE, Emacs + Slime, while extremely powerful, is too intimidating for young students. Another reason is that Common Lisp is a beast and is tough to learn…

Conclusion

Learning by experimenting is the best way to learn. Learning programming using Scheme is fun and rewarding as the language is so malleable. A University is not only a place where people go to get a degree. Rather it’s a place where intelligent people (students + academics) meet to share knowledge. Someone wrote on Slashdot:

“When Plato and Aristotle founded their schools, they didn’t put up a big sign that said “When you’re done, you get more money.” That wasn’t the promise. The promise was that by teaching you about the world, you would become a better person. That is to say, the founding concept of the University was that education lead to human excellence.”

My students will become better persons by experimenting with Scheme :-)