Hi OGs, How can I delete the 1st pair in a map ? Thank you

In Elixir, the order of the keys is persisted if You have less than about 135 keys. I do not remember the exact number… nor where I learned that :slight_smile:

[image] msimonborg: <= 32 [image] kokolegorille: 135 :face_with_monocle:

intereseting fact, but … citation needed.

Hmm :sweat_smile: I only “learned” by playing around in the repl. High probability that I’m wrong :slightly_smiling_face:

I checked, as I do remember it was my first question on the Elixir forum. [image] Nested Set in elixir Questions / Help Hello everybody, I was trying to implement hierarchical tree structure in Elixir. At first I implemented a tree of processes, linked by parent, children…

Final and conclusive solution; always deleting the 1st pair: new_map = %{“name” => “foo”, “address”=> “bar”} |> Enum.into(%{}, fn {“name”, v} -> {“1st”, v} other -> other end) |> Map.drop([“1st”]) ps. try this at home but never at work.

[image] msimonborg: in Elixir small maps (<= 32 elements) automatically sort the keys by Erlang term order, while large maps (> 32 elements) do not At the moment of writing it’s true but one should not rely on it. So we may as well forget it as it’s an implementation detail that might change. …

[image] BartOtten: |> Enum.map(fn {“name”, v} -> {“1st”, v} other -> other end) |> Map.drop([“1st”]) If it wasn’t piping a list into a Map function this would be the definitive way to drop the 1st pair of a map :joy:

If performance is a concern and we don’t want to create a full map from scratch, maybe we could do something like (disclaimer: I didn’t benchmark): {first_key, _, _} = map |> :maps.iterator() |> :maps.next() Map.delete(map, first_key) (“first_key” in the sense of whatever keys comes out first …