Erlang 25 comes with https://www.erlang.org/blog/my-otp-25-highlights/#mapsgroups_from_list23
On Sun, May 8, 2022 at 6:59 PM Aaron Ross <superhawk...@gmail.com> wrote: > I’ve seen this referred to as `key_by` in a few other contexts, such as > lodash <https://lodash.com/docs/#keyBy>. When I was first learning Elixir > from a JS background, I recall looking for a comparable function in Enum a > few times, but I believe the `Map.new/2` approach is idiomatic. > > On Sunday, May 8, 2022 at 7:39:57 AM UTC-7 José Valim wrote: > >> I think a code snippet here would help but it does feel like Map.new does >> most of the job: >> >> Map.new(collection, &{&1.email, &1}) >> >> I am not convinced about the name index_by. I understand the meaning of >> index here, but it is not what index means in Enum (i.e. an integer). >> >> On Sun, May 8, 2022 at 3:31 PM Adam Lancaster <ad...@a-corp.co.uk> wrote: >> >>> Map.new is the right approach in my humble opinion, i’m not sure what >>> index_by would add over that. Keen to hear other opinions though. >>> >>> The function proposed sounds more like “group_by_index” to me but that’s >>> just me. >>> >>> Best >>> Adz >>> >>> On Sun, 8 May 2022 at 14:24, Tobias Pfeiffer <pra...@gmail.com> wrote: >>> >>>> Hello everyone, >>>> >>>> I'd like to propose `Enum.index_by/2` (or potentially /3, see further >>>> down). >>>> >>>> Essentially, it is supposed to be same thing was `Enum.group_by/3` but >>>> without putting the values into a list - so one key, one item. >>>> >>>> It is inspired by the Rails Enumerable method of the same name [1]. >>>> >>>> Now, why should we have this? >>>> >>>> I believe the use case, while not super common, is common enough and >>>> valid. Most often I see it when you have 2 different collections of data >>>> and you want to stitch them together. For instance, you have accounts of >>>> your users on another platform and you want to associate your users to >>>> those accounts - so you fetch your users, index them by their email as a >>>> key and then you can go through the other list effectively fitting them >>>> together with your user. Or take payment transactions in an external >>>> payment system and payment transactions as tracked in your application. >>>> >>>> I'm not aware of a "nice" way to do this in Elixir right now. The >>>> "best" would probably be `Map.new/2` although most often I see people fall >>>> back to `Enum.reduce/3` which I consider sub optimal for most cases >>>> (thankfully most common usages of `Enum.reduce/3` usually have a better >>>> equivalent in the language itself). >>>> >>>> While `Enum.group_by/2` does most of what I want here, transforming all >>>> the one element lists into just the element to easily work with it is >>>> somewhat annoying. >>>> >>>> Speaking of which, it might be fair to say that if we want to do this >>>> we'd want `Enum.index_by/3` to mirror `Enum.group_by/3` (with an optional >>>> value function) which sounds good to me. >>>> >>>> Happy to tackle the implementation myself. >>>> >>>> Thank you + cheers, >>>> Tobi >>>> >>>> [1] >>>> https://api.rubyonrails.org/classes/Enumerable.html#method-i-index_by >>>> >>>> PS: Have a bunny >>>> >>>> [image: IMG_20220130_140748_Bokeh.jpg] >>>> >>>> >>>> -- >>>> 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-co...@googlegroups.com. >>>> To view this discussion on the web visit >>>> https://groups.google.com/d/msgid/elixir-lang-core/CAG3Z5YR3rQL4kcNFACj59i6t7GuBHN34bGCubQ6V8diG47ePLg%40mail.gmail.com >>>> <https://groups.google.com/d/msgid/elixir-lang-core/CAG3Z5YR3rQL4kcNFACj59i6t7GuBHN34bGCubQ6V8diG47ePLg%40mail.gmail.com?utm_medium=email&utm_source=footer> >>>> . >>>> >>> -- >>> 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-co...@googlegroups.com. >>> >> To view this discussion on the web visit >>> https://groups.google.com/d/msgid/elixir-lang-core/CADwgC_BsS8BvjfhxBFkcPfyuv3N_J%3DtcZdT0DfJisoVxbkx0KQ%40mail.gmail.com >>> <https://groups.google.com/d/msgid/elixir-lang-core/CADwgC_BsS8BvjfhxBFkcPfyuv3N_J%3DtcZdT0DfJisoVxbkx0KQ%40mail.gmail.com?utm_medium=email&utm_source=footer> >>> . >>> >> -- > 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/989f7e41-446b-4f63-8106-e9beb20f6b06n%40googlegroups.com > <https://groups.google.com/d/msgid/elixir-lang-core/989f7e41-446b-4f63-8106-e9beb20f6b06n%40googlegroups.com?utm_medium=email&utm_source=footer> > . > -- Kurtis Rainbolt-Greene, Software Developer & Founder of Difference Engineers 202-643-2263 -- You received this message because you are subscribed to the Google Groups "elixir-lang-core" group. 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