+1. I'd also like to mention that other languages don't have any kind of syntactic sugar/special syntax for iterating over keys. That is achieved using a function though.
This proposal to me seems a bit like the "return if/guard" RFC i. e. I see no value in it. On Wed, Sep 2, 2020, 8:13 PM Nikita Popov <nikita....@gmail.com> wrote: > On Wed, Sep 2, 2020 at 5:16 AM Mike Schinkel <m...@newclarity.net> wrote: > > > This is a new thread for John Bafford's RFC which he mentioned on another > > thread, see below: > > > > https://wiki.php.net/rfc/foreach_void < > > https://wiki.php.net/rfc/foreach_void> > > > > Just like the first time this was discussed, I don't think this RFC makes a > sufficient case on why we need explicit syntax for this. Just ignoring the > value is an existing pattern that works across all PHP versions: > > foreach ($iterable as $key => $_) { ... } > > Introducing special syntax for this has costs, both in terms of language > complexity and in terms of implementation complexity. For example, > implementing this feature will make foreach (whether or not the value is > ignored) marginally slower, because we will have to explicitly distinguish > this case. (Or alternatively, we'd have to specialize and increase VM code > size -- it's not free in any case.) > > Iterating over just the keys is not a super common pattern and we already > have a reasonable way to do it (that is imho just as clear, and actually > more concise than the proposed "null" variant). The only potential > advantage to a dedicated syntax that I see is that there could be iterators > that can cheaply produce keys, but have expensive to produce values. That > seems like an edge case of an edge case though, and is a situation where > manually calling ->key() would be justifiable. > > Regards, > Nikita > > > On Aug 31, 2020, at 5:50 PM, John Bafford <jbaff...@zort.net> wrote: > > > > > > Hi Riikka, > > > > > >> On Aug 31, 2020, at 14:13, Riikka Kalliomäki < > > riikka.kalliom...@riimu.net> wrote: > > >> > > >> A common pattern that I've seen that could dearly use PHP internal > > >> optimization, if possible, would be: > > >> > > >> foreach (array_keys($array) as $key) { > > >> } > > > > > > I have a draft RFC (https://wiki.php.net/rfc/foreach_void) and patch ( > > https://github.com/jbafford/php-src/tree/foreachvoid against php 7.0, I > > think) that helps with this, by allowing the following syntax: > > > > > > foreach($iterable as $key => void) { ... } > > > > > > This would iterate over the keys of the iterable, and does not retrieve > > the values at all. > > > > > > In theory, this should be a general performance win any time one needs > > to iterate over only the keys of an iterable, because it does not require > > the use of an O(n) iteration and building of the array that array_keys() > > would, plus it works on non-array types (such as generators or > iterators). > > It also is more performant than foreach($iterable as $key => $_) {}, > > because it omits the opcode that instructs the engine to retrieve the > > value. (Presumably, a future direction could include using this request > to > > inform generators or iterators to only return keys, and not values, which > > could further improve performance, especially if value generation is > > expensive. But that is out of scope for this RFC.) > > > > > > If this is something we'd like for PHP 8.1 and there are no major > > objections to the idea, then after 8.0 is released, I can move the RFC > out > > of Draft and into Under Discussion, and presuming a vote passes, I'll > > update the patch as necessary to work against 8.0. But my time is limited > > and I'm not willing to put further time into the code unless an RFC vote > > passes. > > > > > > Thoughts anyone? > > > > +1 from me. > > > > BTW, your RFC says "Next PHP 7.x" for Proposed Version; might need to > > update that? > > > > -Mike >
