Inspired largely by the example of Larry Wall, the designer of Perl, lots of hackers are thinking, why can't I design my own language? Those who manage to harness the power of the open source community can get a lot of code written for them very quickly.

The result is a kind of language you might call top-heavy: a language whose inner core is not very well designed, but which has enormously powerful libraries of code for solving specific problems. (Imagine a Yugo with a jet engine bolted to the roof.) For the little, everyday problems that programmers spend so much of their time solving, libraries are probably more important than the core language. And so these odd hybrids are quite useful, and become correspondingly popular. A Yugo with a jet engine bolted to the roof might actually work, as long as you didn't try to take a corner in it.

Another result is a great deal of variety. There has always been a lot of variety in programming languages. Fortran, Lisp, and APL differ from one another as much as starfish, bears, and dragonflies, and all were designed before 1970. But the new open source languages have certainly continued this tradition.

I seem to hear about a new language every couple days. Jonathan Erickson has called it "the programming language renaissance." Another phrase people sometimes use is "the language wars." But there is no contradiction here. The Renaissance was full of wars.

Indeed, many historians believe that the wars were a byproduct of the forces that created the Renaissance. The key to Europe's vigor may have been the fact that it was divided up into a number of small, competing states. These were close enough that ideas could travel from one to the other, but independent enough that no one ruler could put a lid on innovation—as the Chinese court disastrously did when they forbade the development of large ocean-going ships.

So it is probably all to the good that programmers live in a post-Babel world. If we were all using the same language, it would probably be the wrong one.

Chapter 11. The Hundred-Year Language

It's hard to predict what life will be like in a hundred years. There are only a few things we can say with certainty. We know that everyone will drive flying cars, that zoning laws will be relaxed to allow buildings hundreds of stories tall, that it will be dark most of the time, and that women will all be trained in the martial arts. Here I want to zoom in on one detail of this picture. What kind of programming language will they use to write the software controlling those flying cars?

This is worth thinking about not so much because we'll actually get to use these languages as because, if we're lucky, we'll use languages on the path from this point to that.

I think that, like species, languages will form evolutionary trees, with dead-ends branching off all over. We can see this happening already. Cobol, for all its sometime popularity, does not seem to have any intellectual descendants. It is an evolutionary dead-end—a Neanderthal language.

I predict a similar fate for Java. People sometimes send me mail saying, "How can you say that Java won't turn out to be a successful language? It's already a successful language." And I admit that it is, if you measure success by shelf space taken up by books on it, or by the number of undergrads who believe they have to learn it to get a job. When I say Java won't turn out to be a successful language, I mean something more specific: that Java will turn out to be an evolutionary dead-end, like Cobol.

This is just a guess. I may be wrong. My point here is not to diss Java, but to raise the issue of evolutionary trees and get people asking, where on the tree is language x? The reason to ask this question isn't just so that in a hundred years our ghosts can say, I told you so. It's because staying close to the main branches is a useful heuristic for finding languages that will be good to program in now.

At any given time, you'll probably be happiest on the main branches of an evolutionary tree. Even when there were still plenty of Neanderthals, it must have sucked to be one. The Cro-Magnons would have been constantly coming over and beating you up and stealing your food.

The reason I want to know what languages will be like in a hundred years is so that I know which branch of the tree to bet on now.

The evolution of languages differs from the evolution of species because branches can converge. The Fortran branch, for example, seems to be merging with the descendants of Algol. In theory this is possible for species too, but it's so unlikely that it has probably never happened.

Convergence is more likely for languages partly because the space of possibilities is smaller, and partly because mutations are not random. Language designers deliberately incorporate ideas from other languages.

It's especially useful for language designers to think about where the evolution of programming languages is likely to lead, because they can steer accordingly. In that case, "stay on a main branch" becomes more than a way to choose a good language. It becomes a heuristic for making the right decisions about language design.

Any programming language can be divided into two parts: some set of fundamental operators that play the role of axioms, and the rest of the language, which could in principle be written in terms of these fundamental operators.

I think the fundamental operators are the most important factor in a language's long term survival. The rest you can change. It's like the rule that in buying a house you should consider location first of all. Everything else you can fix later, but you can't fix the location.

It's important not just that the axioms be well chosen, but that there be few of them. Mathematicians have always felt this way about axioms—the fewer, the better—and I think they're onto something.

At the very least, it has to be a useful exercise to look closely at the core of a language to see if there are any axioms that could be weeded out. I've found in my long career as a slob that cruft breeds cruft, and I've seen this happen in software as well as under beds and in the corners of rooms.

I have a hunch that the main branches of the evolutionary tree pass through the languages that have the smallest, cleanest cores. The more of a language you can write in itself, the better.

Of course, I'm making a big assumption in even asking what programming languages will be like in a hundred years. Will we even be writing programs in a hundred years? Won't we just tell computers what we want them to do?

There hasn't been a lot of progress in that department so far. My guess is that a hundred years from now people will still tell computers what to do using programs we would recognize as such. There may be tasks that we solve now by writing programs and that in a hundred years you won't have to write programs to solve, but I think there will still be a good deal of programming of the type we do today.

It may seem presumptuous to think that anyone can predict what any technology will look like in a hundred years. But remember that we already have almost fifty years of history behind us. Looking forward a hundred years is a graspable idea when we consider how slowly languages have evolved in the past fifty.

Languages evolve slowly because they're not really technologies. Languages are notation. A program is a formal description of the problem you want a computer to solve for you. So the rate of evolution in programming languages is more like the rate of evolution in mathematical notation than, say, transportation or communications. Mathematical notation does evolve, but not with the giant leaps you see in technology.

Whatever computers are made of in a hundred years, it seems safe to predict they will be much faster. If Moore's Law continues to put out, they will be 74 quintillion (73,786,976,294,838,206,464) times faster. That's kind of hard to imagine. And indeed, the most likely prediction in the speed department may be that Moore's Law will stop working. Anything that's supposed to double every eighteen months seems likely to run up against some kind of fundamental limit eventually. But I have no trouble believing that computers will be very much faster. Even if they only end up being a paltry million times faster, that should change the ground rules for programming languages substantially. Among other things, there will be more room for what would now be considered slow languages, meaning languages that don't yield very efficient code.