One of my friends is workingthrough SICP. (He left his job becauee he felt burnt out and wanted to do something different before he went back into a 9 to 5 job). He is posting the answers on his blog (http://lawfulsamurai.blogspot.com/search/label/SICP). This might be helpful to you
This is my favorite version of vim on OS X. It uses Cocoa and is fast. There's a pre-built .app in the tarball on that site and a script to launch macvim from the command line.
The problem is, there might be new comments even if you visited the thread.
But there's a remedy for it and it's simple: the link includes the number of comments in that discussion, so that your browser can change the color if the number of comments has changed since your last visit.
Q. Why don't you have some kind of system so I can see what posts I've already read?
A. We have the best system that can be implemented in a distributed, scalable fashion: we let everyone's browser keep track of it. Web browsers will change the color of the links you've already visited from blue to purple. So all we have to do is subtly change the URL for each topic to include the number of replies available; that way when there are additional replies the post will appear in the "unread" color again.
Anything more elaborate than this would be harder to build and would needlessly complicate the UI.
Very clever. I may do that. But it would take more than 5 seconds, because I have to think about the best way to distinguish between visited and unvisited links.