Seibel: So you and Kay followed, as you say, separate paths. Did you become disenchanted with the original Smalltalk vision?

Ingalls: No, not at all. I’ve talked about my training as a physicist, and I think it’s in my nature to look at the world—how it works, how forces are, how the planets move, how the winds blow, and all that stuff—as asking questions about it and really being in touch with the phenomenon. In the physical world, at least, that’s easy. You can zero in and come away with an understanding of, “Yes, that’s how it works.”

In computers I think there’s the same kind of thing. You should be able, in a computing environment, to zero in on music and musical synthesis and sound and just understand how the whole thing works. It should be accessible. The same thing with graphics. It’s put together very much the same way. You’ve got atomic things, which are the various graphical effects, and then you’ve got structural things you put them together with. The same thing’s the case for numerical calculation.

When I take somebody new with Smalltalk, I’ll say, “What interests you, taking text apart? Playing with numbers? Looking at graphics? Or playing with music?” And then we start there and do a deep dive on that. It’s very much still a part of my passion, and I’m sure Alan’s too, to take people through some deep dive in a direction that they’re motivated about so they come away with what Alan calls powerful ideas—the “aha!” that lets you see this amazing variety is really a couple of small, general things at work.

You can see that in music. You can see it in graphics. You can see it in numbers and text manipulation. And it’s really exciting to me to make that available and accessible.

The Squeak environment is really a computer scientist’s environment. The eToys environment is a kids’ environment, but not as comprehensive as it could be, and I still feel there’s a thing we haven’t done out there, which would allow you equally intuitively to dive in and get a physical understanding of those powerful ideas.

I’m still as passionate about that as anything. Why I’m here doing this stuff—JavaScript and the browser—is that we’re getting pretty close to being able to put Squeak-like material on a web page that you can browse from any browser and interact with in some nice, self-revealing way. That’s part of this whole picture. I’m sure it’s going to change. Browsers are going to change. We’ll get other languages besides JavaScript, and I’m still totally in touch with Alan and his group, who are doing another take on this going deeper down and trying to solve some of these other things more seriously. But it’s absolutely still the same vision.

Seibel: You mention four disciplines: music, graphics, mathematics, and text. Those are about as old as humanity. Clearly there are powerful ideas there that are independent of computers—the computer just provides a way to explore them that might be hard without the computer. Is there also a set of interesting, powerful ideas inherent in the computer? Is programming or computer science another deep discipline—a fifth area—that we can only do now that we have computers?

Ingalls: Yes, I think that’s what I am getting at. The curriculum I’ve always envisioned is one in which you start with one of these and maybe from the motivation of going deep in one of those areas, you move over to one of the other ones that’s less familiar and do a similar thing there. And a lesson to be learned is that the way in which you get to those simpler, deeper structures that generate that whole field is similar in every case.

There’s an algebra of graphics. It’s primitive objects, superposition translation, rotation. Or music. It’s notes and temporal sequences and chordals—same thing. And I think this goes back to seeing how the wind works and how the planets move. It’s an invitation to go down and find out how things work and learn the things that make up the algebra—the processes and the primitive things. So yes, that fifth area, as you call it, is just what’s common about all of these things.

Seibel: Would you expect someone who has played with three or four of these areas to end up learning how to program? Or is that just one of the things that could happen if their interest happened to go down a particular channel?

Ingalls: I think it’s just one of the things that could happen. Hopefully you’ve sharpened their thinking skills. Both by introducing them to stuff and by getting them excited about stuff in some way or another. But there are people who are going to like programming and there are people who are not. I’ve got a 12-year-old son and all he wants to do is do 540s on skis, and there’s a time and a place for everything.

Seibel: Back to some nitty-gritty: how do you test your software?

Ingalls: It depends what I’m doing. I always set it up for the most immediate gratification. So when trying to do something new, I just think of what would be the first piece of success that’s achievable. And it’s different in every case. If I had a more normal life, in more normal programming teams, I’d probably be totally into the current way of team programming. But for me, it’s much more self-induced—even down to a question of my attention span. If I think I could get this working over the weekend, then that’s the chunk I pick and that’s the thing that I go flat out for, ignoring all the other things. It’s hard for me to generalize this except to say, there’s a place you want to get to, you pick a piece of it that would be gratifying and that would demonstrate that you’re on the path and that you can fit into the time until you next get pulled off to do this at home or that at work.

Seibel: Since you’ve picked something that’s going to have some kind of gratifying result at the end, that’s your first test—an acceptance test: does it draw a window on the screen or whatever? What about finer-grained tests?

Ingalls: If it’s the first time you’ve made it possible to pick something up and drag it over and drop it down, there’s a framework that you need to have working there. Is the framework factored so that someone else coming along will see that these are the tests? That’s something that I have not typically done. This may just be the luxury of my generation—nobody would get away with that these days. But I’m an old fart and they’re not going to make me do it. But I think the underlying feeling is still the same. The Squeak code used to be full of comments that are executable and things to check. For instance, in lots of the BitBlt tests, there are these little things that will pick something up from one place on the screen, do something to it, and put it back, and if you see anything change on the screen, it’s not working right and the comment says so. That’s a straightforward test.

Seibel: So let’s talk about working with others. The Learning Research Group at PARC sounded like a pretty close-knit group. How did you collaborate on the code itself?

Ingalls: Just by being close. And occasional mayhem. It was never a big group and we each had our own areas. There’s a lot of team programming expertise that’s grown up and I’m not up on it at all. Right now, in the Lively Kernel, the kernel part has been just me and one other guy, Krzysztof Palacz. And we sort of have our separate areas that we work on. We actually do use a code repository now, and there are other guys on the team who are doing more application stuff and a little bit in the kernel. And I see that it’s nice having a shared repository that works—that’s great. The next step for the Lively Kernel is to integrate it with the repository—you can change stuff in the Lively Kernel but it’s only that running version; it doesn’t get pushed out to the repository and become a part of the future. That’s the next step we need to do.