Yesterday I took a look at E. It’s a special language.

The things that make it so special are his security-by-design and the concept of promise. A promise is somewhat like a deferred in Twisted domain. The language assures you that it will call the remote method in an asynchronous manner and tell you when data is ready (see Dataflow concurrency, lazy evaluation and Oz)

See what the documentation of E says:

The promise architecture described here is the heart of what makes E different. There are no multiple threads, no synchronize statements, no critical objects, no deadlocks. Yet the promise architecture allows the construction of all the different distributed programming behaviors that more conventional architectures allow. The consequence is that distributed systems written in E are more robust and easier to work with– once you have grasped the implications of promises.

The current implementation sits on top Java (it won’t work on 1.5 but on 1.4 runs fine) and seems quite slow. There is another on-going implementation on top of Common Lisp and by now it’s slower because uses parts of the Java one.

If you are somehow interested in concurrency it’s worth a look.