Java Growing?

I’ve mentioned several times on this blog that the lack of new features in C++ makes me nervous. I’ve not seen Java grow much either, but that may have more to do with the blogs I look at. I saw this on Gosling’s blog, the creator of Java (and many other things — like emacs):

Java feels alive, not stuck in some chisel marks on stone tablets. Closures were left out of Java initially more because of time pressures than anything else. Closures, as a concept, are tried and true – well past the days of being PhD topics. The arguments are in the details, not the broad concepts.

I am very happy to see this sort of thing. Programming languages should be living things.

Closures are a very cool concept, btw. They come straight from functional programming, and they make it very easy to design call-backs in complex systems. Basically, I can write the following (in no particular syntax of any language that exists today – that I am aware of):

int x = 0;

vector<int> junk;

… fill the vector of int’s junk with some values…

junk.foreach (doit (int val) { x = x + val; });

I define this inner function “doit”, which is passed as an argument to the foreach method of the vector junk. The foreach method calls “doit” for each value. And do it adds to x the value generating the sum. Anyone that has used STL and the std::for_each algorithm function knows the kind of pain it causes: if you have to maintain any state between each call you end up having to create an object. In C++ that is a lot of syntatic overhead. Closures almost totally eliminate that. I’ve used the C# language, which has closures, and writing this sort of code just flows from your finger tips – in C++ you have to fight to get the code to come out, your source files become huge, and you generate all these objects you never reuse.

Maybe someday soon C++ will have this as well. That would be sweet and would make STL a whole lot more powerful — and most importantly — easy to program.