[Python-Dev] PEP 380 (yield from a subgenerator) comments

[Greg Ewing]

Guido van Rossum wrote:

> The way I think of it, that refactoring has nothing to do with
> yield-from.

I'm not sure what you mean by that. Currently it's
*impossible* to factor out code containing a yield.
Providing a way to do that is what led me to invent
this particular version of yield-from in the first
place.

I wanted a way of writing suspendable functions that
can call each other easily. (You may remember I
originally wanted to call it "call".) Then I noticed
that it would also happen to provide the functionality
of earlier "yield from" suggestions, so I adopted that
name.

But for me, factorability has always been the fundamental
idea, and the equivalence, in one particular restricted
situation, to a for loop containing a yield is just a
nice bonus.

That's what I've tried to get across in the PEP, and
it's the reason I've presented things in the way I have.

> It's not just variable references -- I used "scope" as a
> shorthand for everything that can be done within a function body,
> including control flow: try/except/finally,
> continue/break/raise/return.

Same answer applies -- use the usual techniques.

When I talk about inlining, I mean inlining the
*functionality* of the code, not its literal text. I'm
leaving the reader to imagine performing the necessary
transformations to preserve the semantics.

> Maybe you're confusing motivation with explanation? That feedback
> seems to tell me that the *motivation* needs more work; but IMO the
> *explanation* should start with this simple model and then expand upon
> the edge cases.

Perhaps what I should do is add a Motivation section before
the Proposal and move some of the material from the beginning
of the Rationale sectiomn there.

-- 
Greg