On Tue, May 30, 2017 at 12:16 PM, Björn Larsson <bjorn.x.lars...@telia.com> wrote: > Den 2017-05-30 kl. 19:58, skrev Levi Morrison: >> >> Internals, >> >> The previous discussion thread has died down significantly and so I'd >> like to start a new one to refocus. This message has some redundant >> information by design so people don't have to reference the other >> thread so much. >> >> Based on the discussion there are a few different syntax choices >> people liked. Overall it's a feature that people seem to want but >> everyone seems to prefer a different syntax choice. >> >> 1. fn(params) => expr >> 2. function(params) => expr >> >> 3. (params) ==> expr >> 4. (params) => expr >> >> Note that 3 and 4 require a more powerful grammar and parser and that >> 4 has ambiguities. I think we can work around them by rules -- only >> mentioning it because its popular because of JavaScript and do not >> prefer this at all. >> >> Note that 1 requires a new keyword. >> >> Option 2 looks the best from that perspective but is by far the >> longest; remember people are partially interested in this feature >> because they want shorter closures which this doesn't really help. >> >> This is why everyone is so divisive. All options have drawbacks. >> Additionally some people don't like binding by value and would prefer >> ref, and others really would be against by-ref. >> >> Which brings me to an option I don't think was ever discussed on list: >> >> 5. >> [](params) => expr // binds no values >> [=](params) => expr // binds by value >> [&](params) => expr // binds by reference >> >> It has quite a few good qualities: >> >> - No new keywords >> - Can choose between reference and value >> - Concise >> - Has precedence in C++, a major language >> - Can be done in our existing grammar and parser[1] >> - Can be extended to allow explicit binding of variables: >> // all equivalent >> // y is bound by value, array by reference >> [&, $y]($x) => $array[] = $x + $y >> [=, &$array]($x) => $array[] = $x + $y >> >> And of course it does have downsides: >> >> - Symbol soup (it uses a lot of symbols) >> - A minor BC break. Empty arrays which are invoked as functions are >> currently guaranteed to be errors at runtime and would have a new >> valid meaning. Here's an example from inside an array literal: >> >> // error at runtime previously >> [ []($x) => $x ] >> // now an array with one item which is a closure that returns >> its parameter >> >> Sara pointed out that we'd need to keep a leading `=` or `&` in the >> array to disambiguate from our array closure form. >> >> Overall I'd prefer 1 or 5. What do you guys think? >> >> >> [1]: I'm pretty sure it can be done but until it's done I can't say >> so confidently because sometimes there are things lurking in our >> grammar I forget about. >> > As I said in the old thread, option 5 with ==> instead of => might > be an option. I think that would mitigate the minor BC break. > > r//Björn
The compatibility issue is with `[](params)` is that it is currently an empty array literal that will be invoked; this is guaranteed to be an error at runtime so it is unlikely to cause much trouble. A trailing `==>` would not help here. -- PHP Internals - PHP Runtime Development Mailing List To unsubscribe, visit: http://www.php.net/unsub.php
