On Sat, Nov 22, 2014 at 10:40:37AM +1100, Chris Angelico wrote:
Let's suppose you use a Python-like macro language to generate Python code. In the macro language, you can write stuff like this:
Is there really any point in hypothesing imaginary macro languages when we have a concrete and existing language (Python itself) to look at?
[snip made-up example]
This is a reasonably plausible macro language, right? It's basically still a class definition, but it lets you leave out a whole bunch of boilerplate. Now, the question is: As you write the simplified version, should you ever need to concern yourself with StopIteration?
Sure, why not? It is part of the concrete protocol: iterators raise StopIteration to halt. That's not a secret, and it is not an implementation detail, it is a concrete, public part of the API.
I posit no, you should not; it's not a part of the macro language at all.
This is why talking about imaginary macro languages is pointless. You say it is not part of the macro language. I say it is. Since the language doesn't actually exist, who is to say which is right?
In real Python code, "raise StopIteration" does exist, and does work in generators. Sometimes the fact that it works is a nuisance, when you have an unexpected StopIteration. Sometimes the fact that it works is exactly what you want, when you have an expected StopIteration. You seem to think that allowing a generator function to delegate the decision to halt to a helper function is a Bad Thing. I say it is a Good Thing, even if it occasionally makes buggy code a bit harder to debug.
and of you are writing a generator, presumably you know how it's going to get use -- i.e. by somethign that expects a StopIteration -- it's not like you're ignorant of the whole idea.
Not necessarily. Can we get someone here who knows asyncio and coroutines, and can comment on the use of such generators?
What about them? I don't understand your question.