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In-Reply-To: <BBCFAF73-61B3-49F3-B9C8-750457321E26@gmail.com>
Date: Fri, 1 Sep 2017 21:02:29 +0800
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 <BBCFAF73-61B3-49F3-B9C8-750457321E26@gmail.com>
To: Rowan Collins <rowan.collins@gmail.com>
Feedback-ID: bizesmtp:lvht.net:qybgforeign:qybgforeign4
Subject: Re: [PHP-DEV] add Fiber (sackful coroutine) support
From: i@lvht.net (Haitao Lv)


> On 1 Sep 2017, at 20:45, Rowan Collins <rowan.collins@gmail.com> =
wrote:
>=20
> Is this your own invention, or is the name and semantics based on some =
existing language or computer science theory? "Fiber" makes me think of =
strings, rather than coroutines, so maybe I'm missing a key metaphor =
here.

Fiber is a lightweight thread. Please see =
https://en.wikipedia.org/wiki/Fiber_(computer_science)
And ruby support Fiber. Please see =
https://ruby-doc.org/core-2.4.1/Fiber.html

>=20
>>> <?php
>>> function foo($a)
>>> {
>>>  $b =3D await $a + 1;
>>>  echo $b;
>>> }
>=20
> Should "await" be "yield" here? If not, what happens if I call foo() =
without being inside a Fiber?

No. A function with a yield will always return a Generator object. A =
fiber with await will return any
value. You can see the await as a resumable return. The value after it =
will be returned and the function
will be paused.

>=20
> Similarly, if I run bar() and it runs foo(), what result will I get =
outside a Fiber, since bar() has no yield, so is not itself a generator?
>=20
>=20
>> So the Fiber API is a little like the Generator API, but is more =
simple
>> yet powerful. So there
>> is no need to distinct $generator->current(), $generator->send(), and
>> $generator->getReturn().
>=20
> Your ->resume() doesn't seem to do anything a normal generator can't, =
except that the yield is nested deeper.

The await is a nested deeper yield!

> Nor does it seem to replace getReturn().

<?php
$f =3D new Fiber(function ($a) {
 return 1;
});

echo $f->resume(); // will output 1

> Meanwhile, how does this relate to other ways of combining generators, =
such as "yield from"?

You can use Fiber to implement a more simple generator, because fiber =
can be paused/resumed in its deeper
call.

<?php
function bar()
{
  foreach ([5,6] as $i) {
    await $i;
  }
}
function foo()
{
  foreach ([3,4] as $i) {
    await $i;
  }
  bar();
}
$f =3D new Fiber(function ($a) {
  await 1;
  foo();
});

echo $f->resume(); // will output 1
echo $f->resume(); // will output 2
echo $f->resume(); // will output 3
echo $f->resume(); // will output 4
echo $f->resume(); // will output 5
echo $f->resume(); // will output 6