>> >> Since generators are shallow, it seems clear that there >> should be some local cps-style transform of generators into the >> remainder of the language. However, it would be a relief to know what >> that cps-style transform actually looks like, and what edge cases it >> has. Anyone care to post a proposal? > > Can't be done without defining the entire language in CPS. Yes, it's > shallow, but a captured activation can involve any arbitrary > combination > of expressions other than function call.
I've done meta-circular implementations of generators (or something like them) twice now. It's amateur work ;) so put it in the FWIW category, but in case you find it useful "research": A) http://www.neilmix.com/narrativejs/doc/ This does source transformation of code into suspendable/resumable "partial continuations" (see http://groups.google.com/group/narrativejs/browse_thread/thread/9e4ade2924bd8ab0 ) This project was more ambitious than implementing generators since it was capturing multiple stack frames. Even so, I found the most difficult part of the transformation to be handling flow control without goto. I'm pretty sure that I never got it quite right, especially in exception handlers that contain break or continue. B) http://neilmix.googlecode.com/svn/trunk/generators/js.js A meta- circular implementation of a JS evaluator that supported generators (intended to be used with function.toString(), so the parser is overly forgiving, ignore the parser.) My strategy in this one was to parse into "bytecode" and run in a mini- interpreter for the bytecode. This was way easier because you get to use goto in the interpreter and the current state of the interpreter can be captured in a closure, making it easily suspendable/resumable. It was also much easier to discover and fix the bugs that I never even considered in narrativejs. _______________________________________________ Es-discuss mailing list Es-discuss@mozilla.org https://mail.mozilla.org/listinfo/es-discuss
