Hi Dmitry,
I'm fine if you'll improve my patch (It's mainly yours :)
I updated my closures RFC: http://wiki.php.net/rfc/closures I have based my new version of the patch on yours (Dmitry), but I made some changes to that: * Objects instead of resources are used, two new files zend_closures.[ch] are added where the new Closure class is defined. Currently, it contains a dummy __toString method that in future may be extended to provide enhanced debugging info, also further additional cool stuff could be added to such a class later on. But I prefer to only add the basic closure functionality at first - you can always extend it once it's there. * I have *not* added any __invoke() magic to normal objects. This is mainly due to the simple reason that adding that would not help a closure implementation at all. Closures need some engine internal magic (use a dynamically created op_array instead of looking one up, setting the correct class scope and setting the correct EG(this). And as I said: I want to stick with the closure basics for now. That said, I do like the possibility of invoking objects directly, so I suggest someone created an additional proposal for that? * I've added a patch for PHP HEAD (PHP 6.0). This is due to the fact that Dmitry's variant of my patch has far less intersections with the unicode functionality than my original patch, so it was quite straight-forward to do so. * Lexical vars are now copied instead of referenced by default. Using & in front of the var, the behaviour may be changed. I added that in order to demonstrate that both was possible and that a simply change of grammar suffices. In my eyes this is the main issue where a discussion has to take place (i.e. copy or reference by default? possibility to change default via syntax? which lexical syntax?) before the proposal can be accepted. * I provided patches for both lexical $var and use ($var) syntaxes. * I provided a patch variant that only stores $this if $this is explicitely used inside a closure (or a nested closure of that closure). This works since it is possible to detect whether $this is used at compile time. For this, I have added a this_used flag to the op_array structure. * I added tests (Zend/tests/closures_*.phpt) that ensure the correct behaviour of closures. [Note that I created my own local SVN repos for developing these patches because I was fed up with CVS's inability to local diffs and locally mark files as added to include them in the diffs. Just to explain the format of the patch.] Anyway, feel free to discuss. In my eyes, the following questions should be answered: * Do you want closures in PHP? I have not seen a single negative reaction to my proposal, so I assume the answer to that is yes. ;-) * Which syntax should be used for lexical variables? Should references or copies be created by default? This is far trickier. First of all: There must *always* be the _possiblity_ to create references, else you can't call it closures. Second: I prefer the 'lexical' keyword, but I could live with the use solution [function () use ($...)]. Third: There are several arguments against default referencing: * (use syntax) As they look similar to parameters and normal parameters aren't passed by ref, this could be quite odd. * Loop index WTFs (see proposal) * Speed? (You always read that refs are slower in PHP than normal variable copies. Is that actually true?) * While it is possible to simply add an & in front of the variable name to switch to refs in "no refs default" mode, there is no obvious syntax to use copies in "refs default" mode other than unsetting the variable in the parent scope immediately after closure creation. Fourth: There are several arguments for default referencing: * (lexical syntax) global also creates a reference, why shouldn't lexical? * Other languages *appear* to exhibit a very similar behaviour to PHP if PHP created references. This is due to the fact that other languages have a different concept of scope as PHP does. Although the list of against arguments appears to be longer, I do prefer using references by default nevertheless. But that's just my personal opinion. * Are you OK with the change that $this is only stored when needed? I don't see a problem. Dmitry seems to be very touchy (;-)) about changing op_arrays but in this case it's only a flag so I don't see a problem for opcode caches (in contrast to a HashTable where the opcode cache must actually add code to duplicate that table). * Do you want closures in PHP 5.3? Since the majority of core developers appear to be against it, I presume the answer is no. I will provide a revised patch that incorporates the results of the following discussion for 5_3 and HEAD once consensus or at least a majority regarding the remaining issues is reached. I will also rewrite the proposal to reflect the discussion results and adjust the tests. After that, I hope that someone will commit at least the HEAD version. Regards, Christian -- PHP Internals - PHP Runtime Development Mailing List To unsubscribe, visit: http://www.php.net/unsub.php
