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Date: Wed, 06 Jun 2012 10:55:28 +0200
To: Nikita Popov <nikita.ppv@googlemail.com>, internals PHP
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Subject: Re: [PHP-DEV] Generators in PHP
From: glopes@nebm.ist.utl.pt (Gustavo Lopes)

On Tue, 5 Jun 2012 19:35:14 +0200, Nikita Popov wrote:
>
> Before going any further I'd like to get some comments about what you
> think of adding generator support to PHP.
>

I approve.

A few comments on the current RFC:

* The RFC is too vague.
* You're violating the contract of Iterator left and right. current() 
and key() should return false when !valid(). next() is underspecified. 
valid() refers to a section that doesn't exist. And if you cannot 
implement rewind(), doing nothing is not an option. In fact, if you 
can't implement Iterator in full, you should implement Traversable 
instead. RewindableGenerator could perhaps implement Iterator though -- 
but I find the nature of RewindableGenerator  very strange. Whether an 
iterator is rewindable or not seems to be related to the nature of the 
generator (e.g., is it reading packets from the network). It's not 
something you can wrap a non-rewindable generator and expect it to work. 
So it's a sort of unsafe operation, like a cast in C.
* Overall, the RFC is very underspecified. We never have a formal 
description of what a generator is and exact semantics of it. There is 
no reference to exceptions. What to do if the generator returns 
function. If the generator can be a function method.
* There are missing sections

I suppose this is a work in progress and that you just want to gauge 
the general interest, and I hope you take these considerations into 
account.

-- 
Gustavo Lopes