[VOTE] Generators View as Markdown

Thanks, this is now fixed. It'll throw an exception now, saying
that you can't traverse an already closed generator.

Nothing in the core throws an exception, why would this?!

I'd rather have it skip foreach, maybe producing a warning/notice.
It'd otherwise also be only place generators throw exceptions, which
is a bit unexpected.

Indeed. Even though yield/generator is an iterator internally,
nothing on the language syntax side hints at that. Nothing even
indicates you're using "OO" there.

This is unlike the SplIterators where are you are clearly constructing
fancy objects.

In their most trivial use (i.e. just sticking them into foreach) you
won't notice that generator objects are actually, well, objects. But
still you can work with them as objects and they also expose the
Iterator API. E.g. you can call $gen->rewind() and this will throw an
Exception (if it isn't rewindable at the moment). Do you disagree that
this should throw an exception? Should it throw an error instead? If
not, then why would the same rewind() call done internally in foreach
not also throw an Exception? Why would that throw an error instead?
It's two times the same thing, just invoked slightly different.

Nikita

function &bind(array $keys, array &$row)
{
foreach($keys as $key)
yield $key => $row[$key];
}

$row = [];
$it = bind(['a', 'b'], $row);

foreach($it as $key => &$ref)
echo $key;
echo "\n";
foreach($it as $key => &$ref)
echo $key;

Thanks, this is now fixed. It'll throw an exception now, saying that
you can't traverse an already closed generator.

Nothing in the core throws an exception, why would this?!

To my knowledge all iterator-related functionality is supposed to
throw exceptions (as it is a feature related to the object oriented
part of PHP). At leas this is what a quick search of the code base
gave me. (See http://lxr.php.net/xref/PHP_TRUNK/ext/spl/spl_dllist.c#1248
for example).

"ext/spl" - SPL is not core language. The generators are. Don't throw
exceptions from core features!

In general I agree with core language features shouldn't be throwing
exceptions...
But SPL definitely should never have been its own extension and most
of it should have been core language features - and throwing
exceptions in many of those cases makes perfect sense.

We also have the case of IteratorAggregate throwing exception (which
is a core language feature, not defined in ext/spl):

$ ./sapi/cli/php -r 'class foo implements IteratorAggregate { function
getIterator() { return new stdclass; } } foreach(new foo as $bar) {}'

Fatal error: Uncaught exception 'Exception' with message 'Objects
returned by foo::getIterator() must be traversable or implement
interface Iterator' in Command line code:1
Stack trace:
#0 Command line code(1): unknown()
#1 {main}
thrown in Command line code on line 1

-Hannes

hi!

"ext/spl" - SPL is not core language. The generators are. Don't throw
exceptions from core features!

I would not have a problem with exceptions here. It is much cleaner
than yet another warning.

Cheers,

Pierre

@pierrejoye | http://blog.thepimp.net | http://www.libgd.org

Derick Rethans derick@php.net wrote:

Nothing shows that they are. In any example I saw, I don't even see any

OO syntax/functionality. For me, "yield" is a core syntax keyword,
and
hence: no exceptions.

I was unware PHP was a purist, non-OOP language. What is "OO syntax" anyway? Why can the core not use high-level language constructs too?

Yield is core syntax, but it produces a function returning a generator, which is an object, and since Iterators use Exceptions, it would be stupid for Generators, which are a class of Iterator, not to.

Sent from my Android phone with K-9 Mail.
Andrew Faulds
http://ajf.me/