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

So I’m not saying, “not assembly language.” I’m saying, you should learn some of these other powerful techniques so when you think about how to go forward, you can take advantage of them. In terms of a place to start, immediate gratification has always worked for me. When I want to teach somebody Smalltalk, I usually start with a little dialog: “What interests you most? Are you interested in how to play with text or things you can do with numbers or things you can do with music, or things you can do with graphics?” And start with any one of those.

There’s all kinds of fun stuff you can do taking text apart and putting it together. There’s all kinds of fun stuff you can do with numbers and different bases and floating-point and fixed. And the same thing with music: you can start with notes and put them together in melodies and chords. And with graphics: superpositions and rotations. Any one of those is a rich space to explore. I really think different people think differently that way. Similarly, if you’re going to teach somebody to program a computer, maybe you work with expression evaluation, maybe you work with logic programming. Maybe you do some stuff in user interface. People will light up in one area and that’s where they should go deep.

Seibel:As I understand it, the original purpose of Smalltalk was to teach a kind of programming literacy. Is that something everyone should have, just the way everyone is expected to be able to read and write and do a little bit of math? Should everyone have some ability to program a computer just because it’s a useful way of thinking?

Ingalls:It’s very hard for me to say that anyone should do anything, because I’ve met people that I think are better than me in this way or that way that know nothing about programming. In terms of literacy, the stuff that’s under there is logic and math and yes, people should be able to think logically. But I’d never say that somebody should know how to program, I don’t think. There’s stuff we do in everyday life that’s like programming. You need to know about procedures with steps, that kind of thing.

Computers incorporate some powerful ideas and can bring some powerful ideas to life. The wonderful thing about computers is they bring mathematics to life. So they can be a great tool that way. Now, my feeling about the powerful ideas that are necessary to lead a good life, it’s not clear how many of them are in this space.

Seibel:Seymour Papert wrote in Mindstorms about debugging as an important element of an intellectual toolkit—the idea that the name of the game is not to get the right answer but to get an answer and then debug it.

Ingalls:Oh, absolutely! People should learn to think clearly and to question. And to me it’s very basic. If you grow up in a family where when the cupboard door doesn’t close right, somebody opens it up and looks at the hinge and sees that a screw is loose and therefore it’s hanging this way vs. if they say, “Oh, the door doesn’t work right; call somebody”—there’s a difference there. To me you don’t need any involvement with computers to have that experience of what you see isn’t right, what do you do? Inquire. Look. And then if you see the problem, how do you fix it? To me that’s so basic and human and comes so much from parent to child.

Computers are certainly a medium for doing that. But they’re just computers. There’s a lot of that that will transfer, but to me it’s really big and basic and human, so it’s not like we’re going to enlighten the world just by teaching them computers.

Seibel:Do you remember the first interesting program you wrote?

Ingalls:Oh, let’s see. In each programming experience, there was something that was out of the box. When I discovered VisiCalc, I wrote a spreadsheet to translate English to pig Latin in VisiCalc. That was, to me, interesting, because it used the spreadsheet metaphor as a parallel programming approach. Parsing text that way was fun and enlightening.

Seibel:So VisiCalc had primitives for taking apart strings?

Ingalls:Yeah, you could take apart strings. Maybe what I actually had was Lotus 1-2-3, not VisiCalc, because I’m not sure that VisiCalc had string primitives. I got one of those little Poqet PCs—it was the first truly handheld PC. It ran on two penlights, and I put 1-2-3 on it, and I had a plane flight across the country and I thought, “What can I do in this time?”

Seibel:That must’ve been well after you learned to program, because there obviously weren’t Poqet PCs when you were starting out.

Ingalls:That was later on. The really interesting thing that I did in Fortran was I got a hold of Val Schorre’s paper on META II—just a wonderful, really simple compiler compiler and wrote an implementation of that in Fortran. So all of a sudden this meant you could have other languages in a Fortran only environment. That was the most interesting thing I did in Fortran, because it used Fortran to escape from the world of Fortran.

Seibel:That seems to be a bit of a theme: the pig-Latin spreadsheet, then this, and a hash table in COBOL for your profiler—is there a part of you that just likes cutting against the grain?

Ingalls:I don’t feel like it’s against the grain, but whenever I have a computing environment to play with, I like to try new things in it. That’s what’s been so much fun about doing the Smalltalk systems I did. You start from pretty much scratch and your job is to figure out what to assemble and get working first that will help you to do the next step and build stuff up from there.

In these cases, it was a matter of getting outside the box. That’s a way of asserting that you’ve mastered the thing—if you can do some things that you wouldn’t have thought you could do in it.

Seibel:Can you identify any big changes in the way you think about programming now?

Ingalls:That’s a good question. One thing is we’ve got lots of computer cycles to spend. So I’m comfortable now, as the pejorative saying goes, pissing away cycles to get something done cleanly. But the basic thing hasn’t changed for me at all, which is trying to get clear about what the kernel or kernels are that I have to work with and the goal that I’m trying to achieve.

It’s changed a little bit in that I’m no longer the quantum mechanic in the group that I work in. I’m more at a higher level—that just means that I’m spending a little bit more time on goals and politics than on code. It’s got more to do with creating a context. Until this later phase of my life, I’ve been lucky to be in an existing context where I didn’t have to create it. But every once in a while I still get down and write serious code.

Seibel:I was looking at one of your papers from the ’70s about your Fortran profiler. In the preamble you were very enthusiastic about how that tool changed your programming from figuring out what you were going to write, writing it, and debugging it, to figuring out what you were going to write, writing a really simple version, profiling it, then optimizing it. Do you still work that way?

Ingalls:I definitely go for effects first, bits on the screen or whatever it is, because that’s so motivating, and you often learn something new about what you had wanted to do just by getting a chance to glimpse where it’s going.

Then if profiling is what’s needed, you profile. Or it may turn out you weren’t doing the right thing—that wasn’t quite what you wanted to do, so you changed the goals, or you change how you’re doing it. But when it’s a matter of performance, I still operate the same way. We did a really nice profiler in Smalltalk, and then Squeak, that gave you good feedback that way.