Features of a programming language, whether syntactic or semantic, are all part of the language's user interface. And a user interface can handle only so much complexity or it becomes unusable. This is also the reason why Python will never have continuations, and even why I'm uninterested in optimizing tail recursion.

Thus spoke Guido - as LtU readers already know.

Now, not even four weeks later, it has become clear that turning tail recursions into iterations can be achieved by an innocent little decorator in pure Python. No Rube Goldberg machine(s) in sight.