Re: [RFC] Make sorting stable

Hi Nikita, Thanks for another nice RFC. This was previously discussed in https://externals.io/message/108841, but I > figured it would make sense to create an RFC for this change: > https://wiki.php.net/rfc/stable_sorting > > As before, the implementation approach is to stick with the existing qsort > and use a fallback comparison criterion, which is cheap to implement > internally. The obvious alternative is to use a stable base sort like > Timsort. I gave this a quick try in > https://github.com/php/php-src/pull/5559, > and it does better in some cases (already sorted data) and worse in others > (random data). I don't plan to pursue this direction personally. (It may > also be interesting to use pdqsort as the unstable base, which should make > the "already sorted" case faster.) > IIRC, in PHP 5 sorting was stable. Then PHP 7 made it unstable. That was something to account for when migrating - BC break inside. Do you know why did this happen at the time? On my side, I would very much prefer a new sorting flag, to be 200% sure of the behavior: sort($array, SORT_STABLE) That would allow ppl that don't care about stability to let the engine go with the fastest algorithm. WDYT? Nicolas