[Async-sig] A modest terminological proposal

[Yarko Tymciurak]

On Tue, Nov 29, 2016 at 11:39 AM, Thomas Nyberg <tomuxiong at gmx.com> wrote:

> This is in reply to this message in the archives:
>
>     https://mail.python.org/pipermail/async-sig/2016-October/000141.html
>
> Nathaniel Smith:
> > I've found that when talking about async/await stuff recently, I've
> > mostly dropped the word "coroutine" from my vocabulary and replaced it
> > with "async function". I'm writing to suggest that we might want > to
> > make this switch as a community, and do it now, before the next 10x
> > increase in the async/await userbase.
>
> For what it's worth, I 100% agree.
>

...yes.


>
> > *Accuracy*: Speaking of jargon, the term "coroutine" *is* an existing
> > piece of jargon in computer science, and our term and their term don't
> > quite match up. This isn't a huge deal, but it's unnecessary
> > confusion.  According to Wikipedia I guess technically we don't even
> > have "true" coroutines, just "semicoroutines"? And every generator has
> > just as much claim to being a coroutine-in-the-CS-sense as an async
> > function does, but when we say coroutine we don't mean generators.
> > (Except when we do.) This confusion might partly reflect the somewhat
> > confusing transition from 'yield from' to async/await, as demonstrated
> > by the official doc's somewhat confusing definition of "coroutine":
>
> I've personally been very confused lately by python's terminology. I've
> always understood coroutines to have nothing a priori to do with event
> loops, scheduling. For example, I've understood coroutines as being
> objects that allow the following kind of flow (taken from
> https://en.wikipedia.org/wiki/Coroutine#Comparison_with_subroutines):
>

I actually think this _is_ a bit of a big deal.
Looking at things like:

    http://wla.berkeley.edu/~cs61a/fa11/lectures/streams.html#coroutines

and (where generators were inspired from, for python)  the Icon Programming
Language book (e.g. co-expressions, and references to coroutines, e.g.
p.119)

     http://www.cs.arizona.edu/icon/books.htm

I think - really - async  != coroutines, and (as others have said) muddies
the waters,
and kills some clarity.

- Yarko


>      var q := new queue
>
>      coroutine produce
>          loop
>              while q is not full
>                  create some new items
>                  add the items to q
>              yield to consume
>
>      coroutine consume
>          loop
>              while q is not empty
>                  remove some items from q
>                  use the items
>              yield to produce
>
> Python has basically supported this flow since 2.x (apart from the
> terminology issue of semi-coroutines mentioned above which I feel is
> relatively minor).
>
> This big point though is that being scheduled or asyncronous is kind of
> a separate property. Posix threads are implemented by feeding it a
> routine to start things off just like much of python's asyncronous stuff
> is built around coroutines, but I don't feel like the term "coroutines"
> should be merged into both just as routines aren't automatically tied to
> threads.
>
> Personally I think if anything the best possible comparison else where
> in computer science are the haskell thunks which delay execution until
> needed.  That's the first thing I think about when I see how curio is
> setup for example.
>
> I recognize that it is very unlikely that this will change (hey language
> meaning changes over time), but I felt like I should reply after finding
> this thread because I personally have been very confused by the
> terminology used by python. (Personally I've been using coroutines by my
> definition for years using yield/send.)
>
> Thanks a lot for the write-up though. You saved my sanity a little
> bit...
>
> Cheers,
> Thomas
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