Lambda the Ultimate

The ECMAScript group has created some public resources for the Edition 4 design and specification process. We've released a public export of the group wiki and started a public mailing list for discussion related to ECMAScript Edition 4.

Keep in mind this is an ongoing process, and we've preferred to release information early to integrate community feedback into the process. As a result the documents are not in their final state, and none of these documents should be considered authoritative yet.

You'll find most of the activity, and the most up-to-date material, in the proposals section. There's a fair bit of information under discussion and clarification as well.

Here's a small sample of proposals that members of LtU might find particularly interesting:

• proper tail calls
• iterators and generators
• let expressions
• optional type system
• continuation marks
• meta-objects

I recently watched this Google TechTalk video by Peter Seibel on Common Lisp.

Not being very familiar with Lisp, I found it quite interesting, especially the part about how Lisp handles error conditions. If I understand correctly, rather than unwinding the stack immediately, it sends a signal back through which is picked up at a higher level. Then that higher level gets to tell the lower level how to proceed. This seems neat, since as the speaker points out, you don't lose your state while asking the higher levels how to handle the condition.

Since I have not come across this before, it raised a few questions:

How well does this work in practice and are there any caveats?
Could this have been used in more mainstream languages (Java, c#, etc)?
Do other languages handle exceptions in this way?