Sunday, December 9, 2007

How programming languages grow

Q: How do programming languages grow?
A: With pain.

Unless you were lost on a deserted island far away from civilization, you must have heard something about the ECMAScript v4 shenanigans. ECMAScript 4 is the future standard specification for what most people will undoubtedly refer to as JavaScript 2. This forthcoming specification brings a whole slew of features into the JavaScript language, about a decade after the current ECMAScript 3 standard came out. Many of the new features are about facilitating the creation of large programs in the language and improving their safety and robustness. As an intentional side-effect, they maintain and improve the syntactic similarity between JavaScript and Java, so that most young programmers will find it easy to learn and use (in case you didn't know, Java is one of the languages students learn in almost every CS curriculum nowadays).

The breadth of the changes as well as the increased similarity to Java has led some people to protest against them, while they portray the future of their beloved language with gloom and doom. Some members of the ECMAScript standardization committee decided to get off the standardization effort and pursue an ECMAScript v3.1, that is much less ambitious in scope, though still quite vague. These members are Microsoft and Douglas Crockford and while Redmond's move has set off the (usually correct) conspiracy reflexes of the community, Crockford's objections carry more weight to those who pay attention.

Doug Crockford has been known for many things in the JavaScript community, but what I respect most is his simplified JavaScript parser, which is itself written in the same simplified JavaScript. This is the second JavaScript parser in JavaScript that I'm aware of, the first being Brendan Eich's Narcissus. This subset of JavaScript that Crockford advocates for (and is still available in the ECMAScript 4 specification) prefers a more functional style of programming with heavy use of prototypal inheritance, compared to the traditional object-oriented style used in Java and proposed for ECMAScript 4. To cut a long story short, the creator of JavaScript convincingly makes the point that JavaScript must evolve if it is to keep up with the needs of its users, otherwise they will pick something else, like Silverlight or Flex.

In that presentation, Brendan Eich makes a reference to a talk given by Guy Steele in 1998, titled "Growing a Language". It was about the time that the Java community was having a debate about adding generics, operator overloading, complex numbers and other features. In the end some of the proposed changes made it to the standard, like generics, while others like operator overloading, did not. Today another debate is raging in the Java community, about adding closures to the language. Though perhaps less emotional than the JavaScript debate, it is still highly divisive and the reactions are occasionally overboard. It seems changing a language always involves fear, anxiety and pain. Guy Steele's talk provides some insights.

Its been about a decade since that talk, and it shows. No Powerpoint/Keynote slides, just hand-written ones manually placed on the projector. Even the haircut is out of fashion. However the actual presentation is sheer genius. Steele uses the form of his talk to illustrate the point of his argument. In order to demonstrate the difference between small languages and big languages in terms of the programs they can create and the difficulty of their use, he picks a subset of English as a given, all words with one syllable, and every time he needs to use another word he provides a definition. In the same way you provide a class definition of a Person in Java and then go on talking about that person in your business code as if it was a language primitive, Steele makes a talk sound like a computer program and as he confesses in the end, creating that talk was a lot like writing a program.

It may seem weird at first, but as you get the hang of it, it's an eye-opener. Not suitable for computer-language illiterate people of course. Your girlfriend definitely ain't gonna like it. Even the jokes are kinda geeky. Just watch it when you have an hour to spare and nobody is watching you. Then perhaps you might be able to understand Brendan Eich's passion. And do the right thing: use Firefox.

1 comment:

past said...

Regarding Adobe, another way to look at it is that they have two plans, Flex and ES4. If one does not pan out, there is still the other (the "don't put all your eggs in one basket" strategy). In that light, Microsoft appears to be using just one basket, hence they need to take more deliberate actions.

About your contributions to ES4, I'm thrilled to hear you are still participating. I was under the impression that you chose to focus solely on ES3.1, judging by your participation in the mailing list. I haven't seen any heated debates since October and I must confess, I really miss them!

Thanks for the comments, I really appreciate them.

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