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Subject: Re: [PHP-DEV] add Fiber (sackful coroutine) support
From: rowan.collins@gmail.com (Rowan Collins)

On 1 September 2017 14:02:29 BST, Haitao Lv <i@lvht=2Enet> wrote:
>
>Fiber is a lightweight thread=2E Please see
>https://en=2Ewikipedia=2Eorg/wiki/Fiber_(computer_science)
>And ruby support Fiber=2E Please see
>https://ruby-doc=2Eorg/core-2=2E4=2E1/Fiber=2Ehtml

Ah, thanks, that makes more sense now=2E

I note that the examples there all implement it not as a keyword, but as a=
 library function, which maybe makes more sense: whereas "yield" turns a fu=
nction declaration into a generator declaration, "Fiber\yield", as we might=
 call it, is just a function call which can happen anywhere and manipulates=
 some global state=2E

The choice of "await" also feels odd: you're not awaiting the thing on the=
 right-hand side of the keyword, you're sending it somewhere and awaiting s=
omething else=2E


> You can see the await as a resumable return=2E The value after it
>will be returned and the function
>will be paused=2E

Again, this explanation doesn't make sense if you can call foo() without a=
ny Fiber code=2E If there isn't an active Fiber to pause, the "await" line =
can't "return" anything; it will presumably throw an error of some sort=2E

function foo($x) {
     $y =3D Fiber\yield($x);
     return $x + $y;
}
echo foo(1);

The 1 isn't "returned" to the echo, it's passed off to a global function f=
or further processing=2E This makes much more sense to me than implying tha=
t foo() is no longer a normal function=2E


>> Your ->resume() doesn't seem to do anything a normal generator can't,
>except that the yield is nested deeper=2E
>
>The await is a nested deeper yield!

Yes, I understand that, but that seems to be completely unrelated to the A=
PI design of having resume() act as start, continue, and final result all r=
olled into one=2E As I say, I didn't entirely follow the reasoning for allo=
wing return in generators, but if Fibers are used for the same purpose, I w=
ould expect the same concerns to arise=2E

However, I think the comparison to generators may be more distracting than=
 useful, as they seem to be very different solutions to the same or related=
 problems=2E

Regards,

--=20
Rowan Collins
[IMSoP]