Hi, thanks for the proposal! We have added list keysort Exactly for use cases like this, So given the new functions are wrappers around keysort and given the new docs, I would push people towards using keysort first.
On Wed, May 4, 2022 at 22:09 'eksperimental' via elixir-lang-core < elixir-lang-core@googlegroups.com> wrote: > Hi group. > When working on sorting some data I realized that after sorting the > enumerable, I had to map and iterate again to do a data transformation > of the elements. > > So I look for a function that would already do this and I cannot find > it. So by looking at the source code > > https://github.com/elixir-lang/elixir/blob/1907914cf0d9d25b32373d3c8ad6b4b59877baaf/lib/elixir/lib/enum.ex#L3213-L3218 > I see that it is already mapping after the sorting, in order to > return the original values. > So we are unnecessarily mapping once. > > What I propose is introduce Enum.sort_by_transform/4 which takes a > transformer function and applies it to each element in the last map > iteration. > > > sort_by_transform(enumerable, mapper, transformer, sorter) > > > > Sorts the mapped results of the `enumerable` according to > > the provided `sorter` function and later each element is tranformed > > by applying the `transformer` function. >> > > After I'm done with the implementation I see in the documentation I > found that a new section has been added to the docs, (due to the > introduction of `List.keysort/3` in the development version of Elixir. > > https://hexdocs.pm/elixir/main/Enum.html#sort_by/3-performance-characteristics > > Coincidentally, the more performant solution that I proposes here does > exactly what the implementation of Enum.sort_by_transform/4 does. > > https://github.com/eksperimental/elixir/commit/77c7bcea9348c0dfb16d0e94b2b5ba9d239a3cd5#diff-9a538f965f1fdc2cf9780b1008560f05bfa2ff80d145445abe37a0d70d3828a2R3219-R3230 > > So the example in the guide could be simplified as (after removing > the filtering of the id of the products, to make the example easier to > grasp) > > Enum.sort_by_transform(products, & &1.price, & &1.name) > > Additionally (and optionally) I introduce Enum.map_sort_by/3 which > solves the common case of mapping and sorting in one go. > For example to sort the products alphabetically: > > Enum.map_sort_by(products, & &1.name) > > You can see the full implementation here: > > https://github.com/elixir-lang/elixir/compare/main...eksperimental:sort_by_transform > > > Please, let me know what you all think. > > -- > You received this message because you are subscribed to the Google Groups > "elixir-lang-core" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to elixir-lang-core+unsubscr...@googlegroups.com. > To view this discussion on the web visit > https://groups.google.com/d/msgid/elixir-lang-core/6272dd6b.1c69fb81.94f35.199eSMTPIN_ADDED_MISSING%40gmr-mx.google.com > . > -- You received this message because you are subscribed to the Google Groups "elixir-lang-core" group. To unsubscribe from this group and stop receiving emails from it, send an email to elixir-lang-core+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/elixir-lang-core/CAGnRm4KJTYyiD4LRTq048cLwdCQrb46Rswv1qWEHE6_mr5_Cdg%40mail.gmail.com.
