ELS 2009 - my impressions

I've finally got to attend an international Lisp meeting — one more item crossed off the checklist!

The European Lisp Symposium 2009 was held in Milan, Italy, during the 27-29 of May. The program featured some interesting presentations, and while I'm not going to go a complete overview of them all, in this post I'll go over the bits that got into my head the most. This means, don't be offended or ignored if your work (or the work you were expecting to read about) isn't mentioned here. It probably means my mindset isn't properly configured, yet :)

The first day of the conference was just the reception, where I got to meet great people. Among the entire conference I got to meet people I've already read about in the web-o-sphere such as Stellian Ioanescu, Scott McKay, Mark Tarver, Nikodemus Siivola, Pascal Constanza and Christopher Rhodes. I also got to know some nice people I didn't know, including Didier Verna, Jim Newton, Claus Brod and Edward Dogde. António Leitão, my PhD supervisor and program commitee chair, introduced me to Mark Feeley, from Termite and Gambit Scheme, who told me about a Gambit package, JSS (a multithreaded javascript compiler), which I must try when I get back home. Most of all, despite some ideological divergences between some of the participants, the mood was quite pleasant, and joyful. After all, Lisp is supposed to bring happiness to those who use it.

The second day started with a Scott McKay talk on his life's experiences, and mistakes. He has grown a pretty strong aversion to incremental code fixes to correct fundamental problems. Pretty much all he's done made him believe that full rewrites gives us the opportunity to think better about the design, and that we cannot try to simplify the code by extending it. He is also concerned about the current "big thing": concurrency. May languages are addressing it, and Common Lisp is getting behind each day that passes. Clojure tackled it, but it carries the known set of burdens. Scott recognizes the great one-man effort, but wonders if it's easier to improve Clojure or to design a new Lisp and get it right from design. This could rapidly solve, for instance, the namespaces Common Lisp problem (instead of having symbols, packages, labels, macros, symbol-macros, etc, etc (Pascal counted 9 different namespaces), we could have one single namespace). The same goes to the type system, *everything* should inherit from the same root object type.

Mark Tarver gets an almost similar position, but he "strayed away" from Common Lisp, and went looking for answers on both Scheme and Python. Because he couldn't find them, he designed Qi, a language that is supposed to offer what he believes to be the best language features.

I found the presentation on hygienic macros for the unhygienic world quite motivating. By using a few helper macros, Pascal Constanza demoed how we can emulate the former on Common Lisp, which is quite useful, specially if you come from the Scheme world. All at the expense of a few extra language constructs, but not too distracting ones.

Charlotte Herzeel presented an interesting approach to implement Software Transactional Memory (STM): she implemented a (limited, not feature-complete) Scheme interpreted within Common Lisp. Doing this allowed her to have access each memory access point easily (she only has to address cell and vectors accesses. The thing is, by having her interpreter, she easily tapped to the code segments where data access is done, via reflection. So it becomes easy to experiment with STM algorithms.

I found out the industry is not sticking to widespread CL implementations. At least three different companies (mostly related to the CAD/graphics world, but I think it's a coincidence) rely on SKILL, or some adaptation of it. SKILL is a small footprint Lisp-like scripting language, and that makes it appealing for many industrial domains. However, it appears to be quite obsolete, undocumented and unsupported. It was nice, though, to see some successful uses of Lisp.

I was kinda disappointed not to see Kent Pitman, I believe he canceled at the last minute. I was also looking forward to see some Clozure CL people there, I'd like to hear about what they have in mind about Cocoa and iPhone development. They already have a great Objective C bridge, but as a Common Lisp, things are entitled to be much easier, specially in order to produce competitive small products (there's a big niche for small simple applications on MacOS, due to Apple's design principles)

Marco Antoniotti was a great host on Milan. He organized a great banquet at Osteria del Treno, where we all got to share some more insightful comments about the entire conference and more. The day after that, Marco wore the cicerone cap and took everyone that was still in Milan for a great Futurismo Exhibit, where we got to learn some amazing bits of the Italian cultural inheritance (definitely not my area of expertise, but it was quite interesting to try to interpret some works and sell my ideas to the guide, despite failing most of the times :) ). That afternoon we visited the Duomo, a massive cathedral on the center of Milan. The most impressive thing for me was to realize the wow-factor was even greater from inside of it (on it's roofs), than from the outside!

All in all, it was a memorable experience, everything went great (i wasn't even bugged with the wireless access difficulties that so many people were forced to have, since i had the eduroam credentials already set up on my machine!). Next year it'll be in Lisbon, so I'll be attending to. Meanwhile, I'll look forward to go to Italy again on July for the 6th European Lisp Workshop (within ECOOP).