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

Seibel:So your goal is to have that half of the code go away?

Thompson:Well, it would be hidden somewhere. It would apply in a systematic way to the other code. Hopefully. It’s a hard job.

Seibel:Do you like working here at Google?

Thompson:Parts of it I like, very much. But parts of it are just ponderous because there’s money involved in bugs and there’s money involved in lots of the stuff. The size is unimaginable. Like day one you kind of get something crippling along and day two you’ve got two million users. You just can’t imagine such a thing.

Seibel:And you’re actually on the production side. As opposed to being in Google Labs, which might be more akin to your past at Bell Labs.

Thompson:But I’m not actually production either. I’m in projects that will become production. But I don’t babysit them after they’ve gone. Probably my job description—whether I follow it or not, that’s a different question—would be just to find something to make life better. Or have some new idea of new stuff that replaces old stuff. Try to make it better. Whatever it is that’s wrong, that takes time, that causes bugs. If there’s anything in the structure of Google, anything that you can put your finger on that could be done better, try to do it better.

Seibel:I know Google has a policy where every new employee has to get checked out on languages before they’re allowed to check code in. Which means you had to get checked out on C.

Thompson:Yeah, I haven’t been.

Seibel:You haven’t been! You’re not allowed to check in code?

Thompson:I’m not allowed to check in code, no.

Seibel:You just haven’t gotten around to it, or you have philosophical objections to the Google coding standard?

Thompson:I just haven’t done it. I’ve so far found no need to.

Seibel:So you’re doing your stuff in your own sandbox? Do you mostly do your stuff in C?

Thompson:I write mostly in C. I do all my test stuff and toy stuff in C while Google is C++, strictly C++. It’s no big deal programming in C++, but I don’t like it. I resist it.

Seibel:You were at AT&T with Bjarne Stroustrup. Were you involved at all in the development of C++?

Thompson:I’m gonna get in trouble.

Seibel:That’s fine.

Thompson:I would try out the language as it was being developed and make comments on it. It was part of the work atmosphere there. And you’d write something and then the next day it wouldn’t work because the language changed. It was very unstable for a very long period of time. At some point I said, no, no more.

In an interview I said exactly that, that I didn’t use it just because it wouldn’t stay still for two days in a row. When Stroustrup read the interview he came screaming into my room about how I was undermining him and what I said mattered and I said it was a bad language. I never said it was a bad language. On and on and on. Since then I kind of avoid that kind of stuff.

Seibel:Can you say now whether you think it’s a good or bad language?

Thompson:It certainly has its good points. But by and large I think it’s a bad language. It does a lot of things half well and it’s just a garbage heap of ideas that are mutually exclusive. Everybody I know, whether it’s personal or corporate, selects a subset and these subsets are different. So it’s not a good language to transport an algorithm—to say, “I wrote it; here, take it.” It’s way too big, way too complex. And it’s obviously built by a committee.

Stroustrup campaigned for years and years and years, way beyond any sort of technical contributions he made to the language, to get it adopted and used. And he sort of ran all the standards committees with a whip and a chair. And he said “no” to no one. He put every feature in that language that ever existed. It wasn’t cleanly designed—it was just the union of everything that came along. And I think it suffered drastically from that.

Seibel:Do you think that was just because he likes all ideas or was it a way to get the language adopted, by giving everyone what they wanted?

Thompson:I think it’s more the latter than the former.

Seibel:It seems there are a lot of people who say, “Gosh, C++ is terrible.” Yet everyone uses it. For instance, it’s one of Google’s four official languages. Why do folks continue to use it if it’s so bad?

Thompson:I don’t know. I think it’s losing at Google. Now there are more people who don’t like it than like it.

Seibel:And they switch to Java?

Thompson:I don’t know. There’s almost no replacement for it. They complain, but they don’t switch. Graduate students coming out—the people who are hired by Google—know it. So it’s hard to do anything else. That’s the reason it keeps going—it saves a tremendous amount of education, reeducation. It gets people productive faster.

Seibel:Are there other languages that you enjoy, or have enjoyed, programming in?

Thompson:All of the funny languages at one point I’ve taken a step in. Like for solving equations and stuff: Maple and Macsyma, things like that. For strings, SNOBOL. Anyway, I’ve played with dozens and dozens of languages, if they do something that’s interesting.

Seibel:And are there development tools that just make you happy to program?

Thompson:I love yacc. I just love yacc. It just does exactly what you want done. Its complement, Lex, is horrible. It does nothing you want done.

Seibel:Do you use it anyway or do you write your lexers by hand?

Thompson:I write my lexers by hand. Much easier.

Seibel:Have you ever done any literate programming, a la Donald Knuth?

Thompson:No. It’s a great idea, but it’s almost impossible to do in practice.

Seibel:Why?

Thompson:It’s two representations of the same program that are often out of phase and conflict with each other. And there’s no way to resolve it. If something is written well in a programming language, then it’s readable. It suffices. The comments don’t need to be that parallel. The comments are maybe for algorithms, or if you do something tricky it’d probably be more in the form of a warning or something. I’m not a big, gross comment kind of guy. It’s legendary.

Seibel:When I interviewed him, Knuth said the key to technical writing is to say everything twice in complementary ways. So I think he sees that as a feature of literate programming, not a bug.

Thompson:Well if you have two ways, one of them is real: what the machine executes. One of them is not. Only if one is massively more brief way than the other is it worthwhile. If it’s the same volume, you read the one that works. If one is much more terse, much less precise, and you can get out of it what you need, then that’s great. But very often you can’t get out of it what you need—you really need the nitty-gritty and then you go to the other. Depending on what you’re after, you read one or the other. But to try to have microscopic descriptions of an algorithm, one in the programming language and one in English—maybe Knuth can do it, but I can’t.

Seibel:Have you ever read any of his literate programs?