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

Peyton Jones:That was a very small process control and monitoring company. We built hardware and software that sat in microprocessor-based computers that were physically sitting in weigh scale controllers for conveyor belts. One thing I built watched a load cell on a conveyor belt that carried coal; it controlled the speed of the belt and listened to what the load cell was saying and adjusted the speed to make the flow rate what it should be. It was a little real-time operating system, which I wrote in a language called PL/Z. It was a little bit like Algol. I wrote it on a Z80 machine that ran a sort of cut-down Unix called Chromix.

It was a very small company—it was like half a dozen people. Varied up to 15 at times. But because it was small everything was quite volatile. Sometimes we had plenty of money, other times we had none. After two years I’d decided that the entrepreneurial life was not for me. This was my main insight about small companies: to be an entrepreneur you need to get energy from stressful situations involving money, whereas my energy is sapped by stressful situations involving money. My boss was the managing director of this company. The worse things got, the more energetic he would be. He’d come bouncing around and he’d have new technical ideas for software. He was just as happy as a bee. And I realized, that’s what you need, because if it saps your energy, you spend your whole time in a slump.

So I decided that was all much too hard work and looked around for a job and ended up getting a job as a lecturer at University College London. And when I was there I had no PhD, I had no research training. So my head of department gave me time off to do research. Gave me a light teaching load so I could get my research gig started. But I hadn’t the faintest idea what to do. So I would sit in my office with a blank sheet of paper and a sharpened pencil and wait for great ideas. And there was this sort of silence while I would sort of stare around the room waiting for great ideas to come. And nothing much would happen.

John Washbrook, who was himself a senior academic in the department, took me under his wing and he told me something that was very important. He said, “Just start something, no matter how humble.” This is not really about programming, this is about research. But no matter how humble and unoriginal and unimportant it may seem, start something and write a paper about it. So that’s what I did. It turned out to be a very significant piece of advice.

I’ve told that to every research student I’ve ever had since. Because it’s how you get started. Once you start the mill turning then computer science is very fractal—almost everything turns out to be interesting, because the subject grows ahead of you. It’s not like a fixed thing that’s there that you’ve got to discover. It just expands.

Seibel:So you came back into academia but you never did get a PhD. How was that possible?

Peyton Jones:These days getting a faculty post without a PhD would be very hard. This must have been 1982, 1983. I applied to UCL because my sister was studying computer science there and she said, “Oh, there are a couple of lectureships at UCL, why don’t you apply?” Much to my astonishment, I was appointed. I can only assume that at the time there must have been a desperate shortage and that anyone that could give a plausible account of himself, in a computing sense, could get hired. Because otherwise, how did they manage to hire somebody without a PhD?

After seven years at UCL I began to think maybe I should get a PhD. But it was a big hassle writing a thesis, really. But, it turns out at Cambridge you can get a PhD by special regulation, which means that you just submit your published work and, with luck, they say, “You are a fine person who should have a PhD.” So I was just getting geared up to do that when I got appointed as a professor at Glasgow. Full professor. So by that time I was called “Professor” so nobody would know whether I had a PhD or not so I dropped the idea. Robin Milner doesn’t have a PhD; it must be a distinguished company. I’ve stuck like that every since.

Seibel:These days, is getting a PhD valuable? Someone once told me a PhD is really a vocational degree—if you want to be a professor, you’ve got to get one but if you don’t want to be a professor, there’s no point. Do you think that analysis applies to computer science?

Peyton Jones:That part is certainly true. It’s necessary but not sufficient if you want to stick with research as a career—either academic or at somewhere like Microsoft Research or Google’s research labs—a serious industrial research lab. You really need a PhD to get past the starting post.

If you don’t want to pursue a career in research, then I think it becomes a follow-your-heart kind of thing. You’re five times as productive if you’re working on something that makes you enthusiastic. So if you find yourself thinking, “I just love this and I’d just like to have some time to dig into it some more,” a PhD is a fantastic opportunity to spend three years in Britain, or rather longer in the States, just studying something. It’s an incredible freedom really because you’re sort of a parasite on society. If you know you don’t want to do full-time research as a career then the reason to do a PhD is because you’re just enthusiastic and inquisitive and interested. But PhDs are rather strange anyway. They force you to work on your own and produce a substantial thesis that most people won’t read—they’ll read your papers. So it’s an unusual research mode.

Once you’ve finished a PhD you start working much more collaboratively with lots of other people on typically smaller, more bite-sized pieces of work. I think in some ways a PhD is an odd preparation, even for research. Odder in Britain because of its compressed timescale. I think in the States you can be more collaborative for a while until you zero in on your own research program.

Seibel:Speaking of research and academics, functional programming is quite popular within the research community but I think a lot of people outside that community see functional programming as being driven by ideas that, while neat, can be very mathematical and divorced from day-to-day programming. Is that a fair characterization?

Peyton Jones:I think it’s about half fair. I characterize functional programming—that is, purely functional programming, where side effects are somehow really relegated to a world of their own—as a radical and elegant attack on the whole enterprise of writing programs. Things that are radical are by definition not evolutionary from the state of where things are at.

Today “where things are at” is that big companies are pouring immense resources into ecosystems and editors and profilers and tools and programmers and skills and all that kind of stuff. The mainstream is, by definition, deeply practical. Meanwhile this radical and elegant stuff of functional programming has much less of that deep, infrastructural support. But at the same time that doesn’t necessarily make it self-indulgent to pursue it. Because, after all, unless some people are working on radical and elegant things you’re going to end up in a local optimum, incrementally optimizing the mainstream but stuck on a low hill.

So I think that one of the good things about the whole business of academic research is that professors can go off and do sort of loopy things without being asked how it’s benefiting the bottom line. Some will do things that turn out to be fantastically important, and some less so; but you can’t tell which is which in advance! So my big-picture justification for why it’s worth some people, like me, spending a lot of time on purely functional programming, is that it shows promise. I don’t want to claim that it’s exactly the way that everyone will be writing programs in the future, but it shows promise. And actually I’ll make the case that it shows increasing promise. I see it as, when the limestone of imperative programming is worn away, the granite of functional programming will be observed.