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

It’s like if the only tool you have is a hammer and someone gives you a screwdriver, and you say, “Well, this isn’t a very good hammer but I guess I can hold the blade in my hand and whack with the handle.” You have a crappy hammer when in fact you could have used it as a fine screwdriver. So, a combination of open-mindedness and a willingness to apply everything you already do know. And of course, code, code, code! The more you use the language, the faster you’ll learn it.

Seibel:Why do people get so religious about their computer languages?

Bloch:I don’t know. But when you choose a language, you’re choosing more than a set of technical trade-offs—you’re choosing a community. It’s like choosing a bar. Yes, you want to go to a bar that serves good drinks, but that’s not the most important thing. It’s who hangs out there and what they talk about. And that’s the way you choose computer languages. Over time the community builds up around the language—not only the people, but the software artifacts: tools, libraries, and so forth. That’s one of the reasons that sometimes languages that are, on paper, better than other languages don’t win—because they just haven’t built the right communities around themselves.

Seibel:Java strikes me as interesting in that regard because it has two communities. There’s the implementers and systems programmers—people who worked at Javasoft or Weblogic or places like that. Then there’s all the people who use Java and app servers and prebuilt frameworks to build business applications. Those are very different bars.

Bloch:There are multiple communities associated with Java and with other programming languages too. When there aren’t, it’s usually a sign that the language is either a niche language or an immature language. As a language grows and prospers, it naturally appeals to a more diverse community. And furthermore, as the amount of investment in a language grows, the value of it grows.

It’s like Metcalfe’s law: the value of a network is proportional to the square of the number of users. The same is true of languages—you get all these people using a language and all of a sudden you’ve got Eclipse, you’ve got FindBugs, you’ve got Guice. Even if Java isn’t the perfect language for you, there are all these incidental benefits to using it, so you form your own community that figures out how to do numeric programming in Java, or whatever kind of programming you want to do.

Seibel:Do you enjoy programming as much as you did when you were a kid?

Bloch:I do, although not necessarily in the same way. Like many kids, I think, to some degree programming was a refuge from aspects of life that I couldn’t handle. And the other thing is, when you’re young you have boundless energy and you can hack for hours and hours on end.

As you get older and have a family and kids and all that, you have other responsibilities, other important things in your life. And yet, there’s still this undeniable high that comes from writing a program, watching the pieces fall into place and coming up with several beautiful lines of code that are readable, fast, and do what you want.

Seibel:Do you ever find that because of your greater awareness that it’s not just enough to get it to work, that there are all these other issues, that it’s almost more daunting?

Bloch:Absolutely. Books too, by the way. I definitely go into avoidance behaviors when starting things. Starting is the hardest part, whether it’s a program or a book or anything else. On the other hand, sometimes you remind yourself, “Come on Josh; you’ve been doing this for three decades now, you know how to do it as well as most other people, so just go for it.” And you just sort of remind yourself that, “Look, pretty much every other time you’ve tried to do this the results have been good, so they’re probably going to be good this time too.”

Seibel:So you just talked about how as your life experience broadens, it can be a distraction, but are there any things, experiences outside of programming, that you feel have made you a better programmer?

Bloch:Oh, absolutely. I think almost everything you do, if you do it well. Ideas transfer from all over the place. One example that comes to mind is, when I wrote my thesis, I did an analysis of a distributed data structure, the replicated sparse memory. And the basic idea that enabled me to do the analysis came from a chemistry course I had taken. It was the notion of a rate-balance equation: when you have a dynamic equilibrium in a system, you can write equations that say, “Things are entering a certain state at the same rate that they’re leaving it.” I got three simultaneous equations in three variables, solved them, and came up with results that precisely matched the observed behavior of this complicated distributed data structure. This was an idea I stole straight from chemistry and retargeted at computer science.

Many things that you see in life, whether in architecture—the way buildings are constructed, in language—the way that communication occurs, many of these ideas can be retargeted. And, of course, there’s math. Math and programming are pretty darn similar. So keeping your eyes open and being willing to reuse ideas is a good thing.

Seibel:Do you know programmers who are great programmers but who aren’t mathematical or well-educated in math? Is it actually important to have learned calculus and discrete math and all this stuff in order to be a programmer? Or is just more a kind of thinking that you could have even if you hadn’t had that training?

Bloch:I think it’s a kind of thinking that you could have if you hadn’t had that training. But it sure helps. I worked with a guy by the name of madbot, Mike McCloskey. He’s very mathematically inclined but hadn’t taken number theory. He rewrote BigInteger. It used to be a veneer over a C package, and he rewrote it in Java with marching orders to make it run as fast as the Cbased version. He actually pulled it off. In doing so he had to learn a heck of a lot of number theory. He couldn’t have done it if he weren’t mathematically inclined, but he wouldn’t have had to learn it if he already knew it.

Seibel:But that was an inherently mathematical problem.

Bloch:You’re right; it’s a terrible example. But I believe that even for problems that aren’t inherently mathematical, the kind of thinking that you learn in math is essential to programming. For instance, inductive proofs are so tied to recursive programming that you can’t really understand one without understanding the other. You may not know the terms base case and induction hypothesis , but you have to understand these concepts if you’re going to write correct recursive programs. So even if the domain is unrelated to math, a programmer who isn’t comfortable with these concepts is going to have a harder time.

You mentioned calculus—I think it’s less important. A funny thing has happened over the years. It used to be just assumed that if you were an educated person who had gone to college you had to know calculus. And there are a lot of beautiful ideas there—it’s nice to be able to get your mind around infinity in that way.

But there’s a discrete and a continuous way to get your mind around infinity. I think that for a programmer it’s more important to have mastered the discrete way. For example, I just mentioned induction proofs. You can prove something true for all integers. It’s kind of magical. You prove it for one integer and you prove that one implies the next and then you’ve proved it for all of them. And I think that is more important for a programmer than, let’s say, understanding the notion of limits.