Re: RFC Draft: Comprehensions

On Sun, Mar 10, 2019 at 10:45 PM Larry Garfield <larry@garfieldtech.com> wrote: > Hello, peoples. I know it's been discussed once or twice before on the > list, many years ago, but not recently. I therefore feel OK putting forth > the following draft proposal for Comprehensions, aka "compact generators", > in PHP: > > https://wiki.php.net/rfc/cohttps://externals.io/message/61021mprehensions > > <https://wiki.php.net/rfc/comprehensions> > > Sara Golemon has written a preliminary patch that is partially complete > (see the RFC link for details, it's impressively simple), but unfortunately > doesn't have the bandwidth to complete it at this time. I am therefore > looking for collaborators with more knowledge of internals than I (which is > almost everyone) to help finish it up. > > The syntax proposed is also subject to revision if a terser but still > lexer-friendly alternative can be proposed. > > At the moment I'm not calling this Proposed yet, as I don't feel > comfortable doing so until someone else is on board to finish coding it. > That said, if someone wants to weigh in on the concept for now (hopefully > supportively) that's also fine. > > Anyone excited enough to help finish the job? > > (This is my first RFC collaboration, so if you're going to smack me for > goofing something please be gentle about it.) > I've brought up a similar proposal a few years ago, probably around the time generators were first introduced: https://externals.io/message/61021 I think my main point of feedback would be to stick closer to existing PHP syntax, even if it costs us some brevity. I would prefer $gen = [foreach ($list as $x) if ($x % 2) yield $x * 2]; over $gen = [for $list as $x if $x % 2 yield $x * 2]; The latter is nice in languages that generally use "for" for this purpose and generally allow omitting parentheses, but I don't think it's good to introduce this kind of syntax inconsistency in one place. Similarly, I found the ability to omit the "yield" expression somewhat confusing. Especially once you get to nesting $gen = [for $a as $b for $b as $c]; the behavior becomes non-obvious. Also wondering how this part interacts with keys, do you decide whether or not to yield the keys based on whether they are part of the for expression? $gen = [for $list as $v]; // drops keys $gen = [for $list as $k => $v]; // keeps keys Finally, Python makes a distinction between list comprehensions using [] and generator expressions using (). This proposal effectively corresponds to generator expressions, but uses the [] syntax. I'm wondering if that will cause confusion. Regards, Nikita