Channels are also not great when you want to break off / cancel iteration. The overhead also compounds when you compose / chain iterators. Plus the "lag" they

Channels are also not great when you want to break off / cancel iteration. The overhead also compounds when you compose / chain iterators. Plus the "lag" they induce due to context switching, although I think I saw an optimisation (proposal) where the runtime would directly switch from one routine to the other in some cases of channel interactions? Or am I thinking of an other language entirely?