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The Semicolon Wars

Every programmer knows there is one true programming language. A new one every week

Brian Hayes

Lisping in Numbers

My plea for peace in programmerhood would carry more weight if I could present myself as an impartial arbiter, with no stake in the outcome of the language race. But it's time to confess. I too have a favorite programming language, which I cling to like a child with a bedraggled teddy bear. Don't you dare try to take away my Lisp!

Carnage at the breakfast table...Click to Enlarge Image

Without engaging in missionary zealotry of my own, it's hard to explain my fondness for Lisp. I'll just say it's a simple-minded language with one trick that it does very well. Every Lisp expression is a list, evaluated by reading the first element of the list as the name of a function and the remaining elements as the arguments to the function. For example, (/ (+ 3 5) 2) is a program for dividing (+ 3 5) by 2 , where (+ 3 5) is a subprogram for adding 3 and 5 . The value of the entire expression is 4 . The syntax is brutally simple, even primitive, but that's its strength. Lisp evangelists always note that data and programs are represented in the same way, which makes it easy to write programs that manipulate other programs. That's true, but what appeals to me is just the uniformity of the notation. Everything is done the same way, and so there's not much to remember. (One thing I won't mention is the profusion of parentheses (which annoy some people). (What the world needs (I think) is not (a Lisp (with fewer parentheses)) but (an English (with more.))))

In the chronology of programming languages, Lisp comes from the very dawn of time. It was conceived nearly 50 years ago by John McCarthy, now of Stanford University. My own acquaintance with the language goes back 25 years. To persist in using such an antique idiom seems peculiar and affected, like speaking in Miltonic verses. There's something stubborn and curmudgeonly about it. It looks like a rebuke to all the effort expended on programming-language design since the 1950s. Do I really mean to suggest that not one of the 2,500 newer languages has been able to improve on Lisp?

No, I don't. And of course the Lisp I speak today is not the language McCarthy introduced 50 years ago. It has been augmented, overhauled, updated, split into multiple dialects, then reassembled in a standard called Common Lisp. (Still, the parts of the language I like best were there at the beginning and have changed little.)

An International Lisp Conference was held at Stanford a year ago. This was a gathering of the faithful, and naturally there was talk about how to bring enlightenment to the rest of the world. It was also an occasion showing that even advocates of the same language are quite capable of arguing among themselves deep into the night.

At the end of the final session, John McCarthy rose to speak. He looked around at his audience and remarked, "If someone set off a bomb in this room, it would wipe out half of the worldwide Lisp community. That might not be a bad thing for Lisp, because it would have to be reinvented." His meaning, as I understood it, was partly that the Common Lisp standard had stifled innovation. But he went on to say that if he could go all the way back to the beginning, there were things he would do differently. Even the maker of the language did not see it as beyond improvement. I found McCarthy's candor refreshing, but I also had the thought: No, no, don't tamper with it. I like it just the way it is.

I do believe there are real differences among programming languages—better ones and worse ones—and I rank Lisp among the better. When you get to the bottom of it, however, I write programs in Lisp for the same reason I write prose in English—not because it's the best language, but because it's the language I know best.

© Brian Hayes

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