Is there an easy way to sort a list of maps by some key, but if those keys are equal, be able to specify another key (and again if equal, another key, and so on)? E.g. fruits = [ %{ color: "yellow", name: "potato" }, %{ color: "red", name: "raspberry" }, …

I cannot find docs to back it up, but I believe that you want Enum.sort_by(list, &{&1.color, &1.name}).

Thanks @hauleth for all the help you provide :+1: :+1: :+1:

Tuples are ordered by size, two tuples with the same size are compared element by element. Expressions — Erlang System Documentation v29.0.2

How would you control the descending / ascending order?

You negate the terms: Enum.sort_by(list, &{!&1.color, !&1.name})

[image] sodapopcan: Enum.sort_by(list, &{!&1.color, !&1.name}) No, this will sort that list: [{false, false},{false, false},{false, false},{false, false}]. You can just reverse the list. If you want to sort by ascending name but descending color you will have to compute a score or something …

I tried it out before replying—copy/pasted from my terminal: iex(10)> [%{color: "yellow"}, %{color: "red"}] |> Enum.sort_by(&{!&1.color}) [%{color: "yellow"}, %{color: "red"}] iex(12)> [%{color: "yellow", name: "potato"}, %{color: "red", name: "apple"}] |> Enum.sort_by(&{!&1.color, !&1.name}) [%{co…

sort_by is stable if EVERYTHING returns the same value: iex(1)> [%{color: "yellow", name: "potato"}, %{color: "red", name: "apple"}] |> Enum.reverse() |> Enum.sort_by(&{!&1.color, !&1.name}) [%{color: "red", name: "apple"}, %{color: "yellow", name: "potato"}] This should have returned the map wit…

Yes, Both expressions return the original list: [%{color: "yellow"}, %{color: "red"}] |> Enum.sort_by(&{!&1.color}) [%{color: "red"}, %{color: "yellow"}] |> Enum.sort_by(&{!&1.color})

The negation trick works for floats and integers, using minus operator. Not sure how to control desc/asc for other data types. :man_shrugging:

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Sort by multiple values?

Questions & Help Questions

thojanssens1 February 27, 2020, 12:03pm 3

Thanks @hauleth for all the help you provide