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.
