Good question. In short, you can use the macros to hide the context-switching (yielding). You could, for instance, force every function to perform a context s

Good question. In short, you can use the macros to hide the context-switching (yielding). You could, for instance, force every function to perform a context switch right after its called. Since languages like Scheme encode even loops with function call, you're guaranteed to eventually hit a switch point. (And, if you allow other looping constructs, you could use macros to hide a yield inside them as well.)