Re: Pattern matching details questions

On Tue, Feb 4, 2025, at 1:14 PM, Marc Bennewitz wrote: > On 04.02.25 08:51, Rob Landers wrote: >> >> >> On Tue, Feb 4, 2025, at 05:31, Larry Garfield wrote: >>> Hi folks. Ilija is still working on the implementation for the pattern matching RFC, >>> which we want to complete before proposing it officially in case we run into implementation >>> challenges. >>> >>> Such as these, on which we'd like feedback on how to proceed. >>> [1] >>> https://github.com/Crell/php-rfcs/blob/master/pattern-matching/research.md >>> >>> -- >>> Larry Garfield >>> larry@garfieldtech.com >>> >> >> Hey Larry, >> >> Instead of symbols, why not use words? >> >> We already have &&, but it looks like this uses & instead, which is a >> bitwise-and. But the language does have “and” as a keyword. So instead of: >> >> $value is int & &$x >> >> It would be: >> >> $value is int and &$x >> >> Which removes the confusion you mentioned before (also for someone like me who uses >> bitwise-and quite a bit). >> >> — Rob Patterns are deliberately designed as a superset of existing DNF types. You can already have a type of Foo&Bar, so we want the pattern for "instanceof Foo || instanceof Bar" to be the same. That means & and | for conjunctions is necessary. Also supporting "and" and "or" would technically be possible, but wouldn't resolve the issue (since & would still be needed either way) and would just add more complication, confusion, and inconsistency. I don't think that's viable. > Is it possible to use the already added "is", like: > > $arr is ['a' => $a, 'b' => is $b] Would that inner "is" be capturing $b, or injecting $b? It just pushes the same question down a level, and with an LL(1) parser we cannot tell what context we're in. (If we could, there would be no problem.) > Or, to use the already known uniform variable syntax "{$var}", like: > > $arr is ['a' => $a, 'b' => {$b}] That looks like it could be confused with a property pattern, assuming we end up doing that for part 1. In which case, is that "index b maps to an object with one property, and bind that property" or "index b maps to an object with one property, and that property should be the value of $b"? Or "index b maps to the value of $b"? That doesn't seem any less confusing, for the engine or human. --Larry Garfield