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Subject: Re: [PHP-DEV] Re: Generators in PHP
From: larry@garfieldtech.com (Larry Garfield)

On 07/27/2012 07:23 AM, Lester Caine wrote:
> Nikita Popov wrote:
>>> I'll ask again since no one has answered ...
>>> >
>>> >In a different way ...
>>> >Is the only thing that changes the 'function' into a 'generator' 
>>> replacing
>>> >the call to process the data with 'yield'? ( That would be 
>>> 'SUSPEND' in an
>>> >SQL procedure ) ...
>>> >
>>> >So how DOES an IDE work out the flow in order to correctly check that
>>> >variables are defined?
>>> >
>>> >As always, my IDE provides a lot of 'sexy' stuff so that I don't 
>>> need to
>>> >have it built in to the language, and I still can't see how a lot 
>>> of what is
>>> >being loaded in helps with performance which is the only thing that 
>>> I am
>>> >interested in. Performance wise why is yield better than just directly
>>> >calling a function to handle the data?
>> Lester Caine and Alex Aulbach,
>>
>> may I ask you to continue this discussion in a separate thread? I am
>> really interested in constructive responses about the generator RFC,
>> but your discussion is generating a lot of noise, which makes it very
>> hard for me to pick out the few mails that are of interest to me.
>>
>> If you could open a new thread (like "Generator keyword") it would 
>> help a lot.
>
> Nikita - I am looking for a well reasoned argument as to why generator 
> has to be added at all! 'Just because it can be' is not a valid 
> argument, but perhaps you could add to the RFC the performance 
> implication or advantage of what is being proposed. That would at 
> least be some comparison with the current methods of doing the same 
> thing?
>

Anthony had a very good writeup on generators and how they compare to 
iterators last week:

http://blog.ircmaxell.com/2012/07/what-generators-can-do-for-you.html

I think that does a good job of laying out the case for generators as 
"low-effort iterators".

I still think the syntax feels clunky to me, but that's probably because 
I'm not used to it from other languages.

One question, though: It looks based on the voting like finally {} 
blocks are going in.  So... what should happen in the following situation:

function stuff() {
   try {
     foreach (range(1, 100) as $i) {
       yield $i;
     }
   }
   finally {
     print "All done";
   }
}

Does "All done" get printed once, or 101 times?  Similarly:

function things() {
   $i = 1;
   try {
     while (true) {
       yield $i++;
     }
   }
   finally {
     print "All done";
   }
}

That will run indefinitely.  So will "All done" ever print, or does that 
finally become unreachable?

(I have no clue what the behavior "should" be in these cases, just that 
it should be sorted out sooner rather than later.)

--Larry Garfield