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Date: Mon, 03 Sep 2012 15:12:46 +0200
To: Derick Rethans <derick@php.net>
Cc: Rasmus Lerdorf <rasmus@lerdorf.com>, Pierre Joye <pierre.php@gmail.com>,
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Subject: Re: [PHP-DEV] Re: Are exceptions allowed in php
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From: glopes@nebm.ist.utl.pt (Gustavo Lopes)

Em 2012-09-03 13:16, Derick Rethans escreveu:
>> I think the first thing anyone who uses generators must understand 
>> is that
>> they are iterators.
>
> You forget that not even everybody that uses PHP knows what an 
> iterator
> is. For all they care, they have an array they can run foreach() on.
>
>> They should be compared with iterators, not arrays.
>
> They shouldn't be compared with either. They are magical things that
> happen with a "yield" keyword.

OK, you prefer to replace the facts (generators are iterator objects 
and they are introduced as such) with an alternative reality that 
putatively exists (or will exist) in the users' mind. I have no interest 
in a discussion in those terms, especially (1) without any evidence 
indicating such mental model is widespread and (2) given that the 
exceptions you claim to be surprising don't happen but for a programming 
error (i.e. they're not exceptions that need to be caught).

>> With that in mind, the behavior is not surprising for anyone who 
>> knows
>> how iterators and foreach interact.
>>
>> More importantly, there is no other satisfactory solution (except a 
>> fatal
>> error). foreach has no return value, so it has no other way to 
>> signal a
>> failure. If we used a notice or a warning here what would happen is 
>> that code
>> that used generators with an invalid state would, except for the 
>> notice, work
>> as if it had been given an empty iterator. Put another way, it would 
>> fail with
>> only a notice, and continue.
>
> Continue doing what?
>

I've replied here: 
http://www.mail-archive.com/internals@lists.php.net/msg60706.html

-- 
Gustavo Lopes