Bravo! It's so rare to see someone discuss a language's closures precisely, with implementation details, and no handwaving.<p>A lot of the time people use the word to refer to all first-order functions, and in a wishy-washy manner that ignores the radical differences between real-world implementations.
Has anyone here installed a lisp machine emulator on a linux pc? I am wondering where to get the source from. The unlambda page, which according to google hosts the code, seems to be down.