Peter Seibel - Coders at Work - Reflections on the craft of programming

Part of that is about performance but part of it is about just structure and architecture. You may find that some things are hardly ever used and maybe you could just get rid of them by doing things differently. It’s just a different perspective on the thing.

Seibel:It seems that virtually every programmer has a copy of Knuth’s The Art of Computer Programming . Some people have it and it’s just on their shelf. Some people have it and use it as a reference. And some people have it and really read it cover-to-cover. You actually studied with Knuth at Stanford; how much of it have you read?

Ingalls:I loved working with Don and I taught his MIX course for one quarter at Stanford, too, which was also enlightening. I think I’m pretty different from Don, but what I like about him is he’s got a great mathematical mind but also loves to go deep into the bits—the pragmatic parts of things. I, too, love to get into the pragmatic side of things but I’m not as rigorous as Don.

I was trained in physics and to me the problems I work on, or how I work on them, is really much more a physical thing. When I’m talking about other perspectives on programs, I’m really thinking that there’s a thing there that you can touch and feel it vibrate.

If you take the way he worked on TeX, it was very mathematical and beautiful and elegant. Compare that with, say, the first Smalltalk engines: they were very ad hoc. I just put together what was needed. It may be that after a few go-rounds, I started to get some sort of mathematical picture of it, or we did, but it’s different in that regard.

So the truth is, I read a fair amount of his basic data structures stuff, but I’m not a big reader—I’m very much of a doer. If I have a flaw, it’s that I will often do my own of X, Y, or Z rather than reading the literature and knowing about it. It’s usually worked to my advantage I think, but who knows?

Seibel:How much math do you think programmers need to know? Dijkstra claimed that computer science is just a branch of mathematics. And understanding The Art of Computer Programming requires a fair bit of math.

Ingalls:You’ve got to have a logical mind. But I spent a lot of time in the country in Virginia while learning about computers. I always thought that if I wanted to start a computer company in the mountains of Virginia, I’d go find the mechanics. Except in certain fairly esoteric parts, the math isn’t near as important as logic and intuition.

I think of a lot of it as being more architectural: the way the graphics work together with the models; the way things need to be updated or cached. That’s not esoteric mathematics. That said, I do view it as being very much a part of the field of mathematics. To me, the really exciting thing about computers is they allowed mathematics to become a synthetic, not just an analytic art. What I have so much fun doing day to day is a mathematical kind of thing, but it’s creative, generative, synthetic.

Seibel:You say you’re not a big reader. Are there any books you’d recommend?

Ingalls:No. And I’m sure I’m in the minority this way. I was not a big reader as a kid. I would occasionally read things thoroughly and not be interrupted until I was done. There are some papers, absolutely, and I guess with them come some books. Val Schorre’s paper on META II is one of them. There is the LISP 1.5 book. There’s APL, but I didn’t find Iverson’s book to be at all a good way to learn it. A mathematician probably would have. I can’t even remember what I read to learn about it from. But I loved it. So I think spending a bit of time in that language would be like a book to read. Likewise, Smalltalk.

Seibel:So do you still enjoy programming as much as you used to when you started?

Ingalls:Yeah, the programming itself. The last couple of years have been interesting because I’ve been taken away from the environment that I got so used to—Smalltalk and then Squeak—where the tools are just really great. I’ve had to step back a little bit, working with JavaScript in browsers and conventional development environments. It sometimes takes me longer to debug stuff than it used to, but the basic process of getting an idea and making it happen I still really enjoy.

Seibel:Do you feel at all that programming is a young person’s game?

Ingalls:Not really, no. There’s something about being able to survey all the stuff that’s going on, and some of that endless energy that I don’t feel I have the way I used to. But I still love to just take a problem and sit down and pore over it until it’s right. There’s an analogy here: I tried to learn to play piano fairly late in life. People said, “Oh, you should learn when you’re young. You learn so much quicker.” Although I didn’t go very far, my conclusion was that it isn’t that young people learn that much faster; it’s just they have more time. When I would put time in, I made progress.

I feel a bit the same thing with programming. When I look back on earlier times in my life, I had all the time I wanted. I would just work and work. Now there are other things going on in my life and I’ve got responsibilities that aren’t just programming. That undermines a bit of that intense focus.

Seibel:Leaving aside the amount of time you get to spend on it, doesn’t programming require a certain intensity and focus? People talk about flow and how if you get interrupted every 15 minutes, you never get anything done because it takes that long to even start getting the stuff in your brain sorted out.

Ingalls:That reminds me of something I said to somebody way back at PARC. I was starting to have some other responsibilities besides just hacking Smalltalk, but we were also making a lot of progress in making it a really productive system. I kidded that I was racing to improve the Smalltalk environment so that I could continue to get reasonable work done in increasingly short amounts of time. So I’d gotten to where in 15 minutes I could sit down and actually do something useful.

The other part of it is that you work with other people. I work with younger people and it’s great—maybe I spend a bit more time thinking at the level of goals and politics and arranging to make things happen, and they’re making up for what I lack in available time for that deep, deep dive.

Seibel:You have a reputation of being a great guy to work for, when you’re leading a project. How do you lead a team that makes people productive and happy?

Ingalls:I love what I do. And it’s fun to share with other people. These activities can go arbitrarily deep or wide, so it’s easy to find things for various people to work on. I’ve just always enjoyed doing that with other people. There have been times when it’s worked better or not—there are very different phases to this kind of work. There are times when you see everything that needs to be done and it’s just a matter of getting people to do it. And there are other times when you don’t really know what needs to be done and you’re trying to find out. Those are really different phases.

Seibel:Do you have any tips on how to be a good technical leader?

Ingalls:The first thing is being clear about what you’re trying to do. The job is to get a clear vision. If you’ve been around, you can see actually how you’re going to implement that, so you can start to see how that would work out in terms of what various people can do and how it would all fit together.

There have been times when I’ve been working on a project where I could see everything. It felt really powerful because whenever anybody was stuck I could tell them immediately what the next step was, or how to get around it. And people feel that, too, if you know where you’re headed. They can immediately sense it’s all there—he’s got it. And that’s empowering for the team as well.