Stackless has its own Web home.
Stephen Figgins does an excellent jobs of describing the state-of-the-implementation in his February 2002 "Stackless Reincarnate".
Christian, on 31 December 2001: "I hope to make it simpler, split apart Stackless and optimization, and continuations are no longer my primary target, but built-in microthreads. . . . What Python needs is a secure mechanism to switch frame changes at certain times." On 20 January 2003: "Stackless focuses on tasklets and channels, now."
[Schemers emphasize that language's two decades of experience with continuations.] [But compare with Smalltalk control flow ...]
Knuth made the distinction between full coroutines and what he called "semi-coroutines" . Icon has both co-expressions and coroutines, but although the language manual made it clear when you would use one or the other, it didn't stress the foundational difference. ( co-expressions or generators in Icon are Knuth's semi-coroutines. )
Coroutines are fully symmetrical -- control is explicitly passed from one routine to another. Semi-coroutines are asymmetrical -- they always return to their caller ( with a suspended state. ).
Majewski came close to getting Icon- and Scheme- (and eventually Simula- and Forth-)inspired continuations in Python ?.? in ?. He found the Scheme literature only moderately helpful. It was LISPly syntax-free, of course, and largely focused on compilation challenges. However, in his words, "Scheme did have a big role in generalizing from coroutines and generators to the idea that if you had continuations, you could build any kind of control sequencing."
[Explain Stackless and Palm. Also ...]