Re: ARRAY_UNIQUE_IDENTICAL option

Hi Levi Morrison, > A bit off topic, but not entirely: > > In my opinion, adding another flag isn't the _real_ fix. Any function > which does comparisons should take a callable for users to provide any > comparison they wish. An iteratively better API would be: > >     function array_unique<T>(list<T> $array, callable(T $a, T $b): int > $comparator); > > Of course, there are other things like instead of using int for > 0, > -1, 1, we could have used an > enum but we don't have one today. I > just mean the core idea of taking callable is better than mucking > around with flags while also allowing for custom comparison. Note that > it doesn't necessarily prevent optimizations either. For instance, if > they had passed php_compare or some function which represents > `$a > <=> $b`, we could identify that just as we identify a specific flag > and take an optimized pass. 1. Calling php functions from C is fairly slow. Sorting compared to hash maps is also slow If we did want a specialized implementation for user-provided equality criteria, ?callable(T $a): U $iteratee = null would seems more practical to me (Calling a function n times rather than n log n times would be faster, and this would work even for cases such as [$obj->nonObjectField1, $obj->field2->toNormalizedRepresentation()] instead of using a comparator in most cases (by putting both arrays into the internal hash map) (same approach as https://lodash.com/docs/#uniqBy) 2. <=> isn't a stable order for int/string/float (etc) in various ways, so some comparators would have issues and return duplicates. It's possible to implement stable comparisons, but I don't really expect enthusiasm for that https://github.com/TysonAndre/pecl-teds/#stable-comparison 3. I expect a majority of cases could use the ARRAY_UNIQUE_IDENTICAL directly. (or use that on array_map()ped values to find the keys of the original array to use) So requiring the use of $comparator would result in longer code and more possible sources of bugs (e.g. a comparator returning $a - $b might overflow/underflow int if users don't realize <=> should be used) Thanks, Tyson