On Fri, Jul 27, 2012 at 8:09 PM, Nikita Popov <[email protected]> wrote:
>> 5. Are multiple yields allowed? I.e. the rfc mentions something like
>> yield yield $a - what that would mean? I'd allow yield only be applied
>> to variable expression (lval) because double yield doesn't make sense to
>> me, but maybe I miss something.
>
> yield yield $a would basically first yield $a and then receive some
> value (via send) and yield that value again. Nothing you'd normally do
> ;) It was mentioned only as a syntax ambiguity consideration.
>
> Actually I added some additional parenthesis requirements for yield.
> For example you'd have to write the above as yield (yield $a) now
> (which should be slightly more clear). I haven't yet reflected this
> change in the RFC, but I'll add a section on it later.
>
>> 6. “Sending values” section seems to be missing. Especially useful would
>> be to cover what happens with keys there and what is the syntax there -
>> is it just "$a = yield;"? Or does it mean when yield is used in
>> expression it becomes incoming yield? And, last but not least - do we
>> need sending into generators at all?
>
> Yeah, I haven't written that section yet. But it is fairly simple: If
> you go $generator->send($foo) then $foo will be the result of the
> current yield expression. And yes, this also works with keys and
> values. All of the following are valid:
>
> $data = yield;
> $data = (yield $value);
> $data = (yield $key => $value);
>
> The first case is the most common though. I.e. you usually use it
> either as a generator or a reverse generator, not both. But doing both
> is also common for cooperative multitasking etc.
>
> Regarding the last question: I think the feature is worth adding. It
> is a very powerful concept that is hard to implement otherwise. Useful
> in particular for things like parsing and multitasking.
>
>> 6. What happens if you send into a by-ref generator? Is the data sent
>> by-ref then? What if it's an expression that can't be send by-ref?
>
> No, sending is always by-value. By-ref only affects the yielding part.
I now added the mentioned sections:
https://wiki.php.net/rfc/generators#yield_keyword
https://wiki.php.net/rfc/generators#sending_values
I also added a list of error conditions:
https://wiki.php.net/rfc/generators#error_conditions
Sorry for the delay,
Nikita