Lisp Hackers: Edi Weitz

The first post of the series got some very good responses, so I'm continuing it with another very obvious candidate — Edi Weitz. His vast contributions to open source Lisp, made during the last decade, collectively known as Ediware, include the indispensable regex library CL-PPCRE, written on a bet in Hamburg café, and a whole stack of web-related libraries with the most widely used Lisp application server Hunchentoot and HTTP client Drakma. Together with Arthur Lemmens he also co-organizes European Common Lisp Meeting. And that's, surely, not all...

Tell us something interesting about yourself.

Well, I'll leave it to someone else to tell you what's interesting about me. I'll rather tell you what I find interesting in addition to Common Lisp: I collect photo books and I'm doing a bit of photography myself. I like to listen to the music of Frank Zappa and to Jazz. I read a lot. I'm interested in mathematics, especially in set theory.

What's your job? Tell us about your company.

I'm a professor for mathematics and computer science at the University of Applied Sciences in Hamburg. I started this job in September 2011.

Before that, I was a freelance hacker for about 13 years.

Do you use Lisp at work? If yes, how you've made it happen? If not, why?

In my new job, I've been using CL in my math lectures a couple of times and will continue to do so.

In my old job, I've been using CL exclusively for the last six or seven years. As I was working freelance, this was kind of easy — I either had projects where the customer didn't care about the programming language that I used as long as I got the job done, or I was hired specifically for my CL skills.

What brought you to Lisp? What holds you?

I came to Lisp via Emacs Lisp in 1999 or so. What got me hooked was the wonderful book "Writing GNU Emacs Extensions" by Bob Glickstein. It opened my mind for the beauty of the Lisp language family — something I had missed the first time I had encountered Lisp (in university, a few years earlier). The two CL books by Paul Graham and Norvig's PAIP then paved the way for Common Lisp.

What holds me is that I haven't found a better programming language so far — and I don't expect to find one very soon.

What's the most exciting use of Lisp you had?

I don't know if "exciting" is the right word, but it makes me happy that so many people use "The Regex Coach" and like it. I stopped keeping track, but there must have been at least half a million downloads since 2003.

I'm also kind of proud that some of my open source libraries are used by various commercial and research projects around the world.

But probably the most awe-inspiring encounters I had with Lisp were the few occasions when I played around with Genera or watched someone else using it. I think this OS really was a work of art.

What you dislike the most about Lisp?

There's nothing I really dislike about Common Lisp. There are a few warts here and there, but so far I've found nothing that was serious enough to prevent me from being productive.

Among software projects you've participated in what's your favorite?

Working on the Windows port of Piano — an extremely impressive application which has been around for almost 20 years and has been used by almost every aircraft manufacturer in the world. Dimitri Simos, Piano's main author, has been the most enjoyable client I've worked with so far.

Describe your workflow, give some productivity tips to fellow programmers.

I usually just start up the LispWorks IDE and hack away. The best productivity tip I can give is to stick with one implementation and IDE and to invest a lot of time to really learn how to use it — including all the implementation-specific goodies like debuggers, inspectors, steppers, browsers, and so on.

Ediware became hugely popular (by Lisp standards), and with this popularity came a lot of work and responsibility. You seem to have mostly handed over supporting it to Hans Hübner. What's up next for you in the land of programming and Lisp in particular?

I'm planning to give a lecture about the use of AI techniques in games in the next year and I might use some Lisp there. I might also — as a sideline — resume my CL consulting work sooner or later. I don't expect to publish new open source code in the near future, though.

If you had all the time in the world for a Lisp project, what would it be?

When I was still working as a hacker, I always dreamt of finding someone to pay me for working on an open-source CLOS object store — written in pure Common Lisp, OS-independent, portable, not relying on third-party software, fast, reliable, thread-safe, well-documented, etc.

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