I have an list which is like [[1, 5], [3, 12], [4, 10]] i want to change it to a map like below %{ 1 => 5, 3 => 12, 4 => 10 } Currently i am using following code and my question is , is there a better way to do. i mean if there is more concise way, or may be a built-in function to do so. Enum.r…

I would not use Map.put or Enum.into because that means that the runtime copies the map, adds one more pair to it, then throws out the previous one – N times. That’s very inefficient. Go with what @NobbZ suggested: it basically says “construct a new map using this list and then use this function (t…

While Enum.into is the simplest, You could have rewritten your Enum.reduce like this. list = [[1, 5], [3, 12], [4, 10]] Enum.reduce(list, %{}, fn [k, v], acc -> Map.put(acc, k, v) end) # or the for version of it for [k, v] <- list, reduce: %{} do acc -> Map.put(acc, k, v) end

It’s quite uncommon to use a list of lists like this, a more common approach would be to have the list as a list of binary tuples. So if you have control over the shape of the incoming list, make it [{1, 2}, {3, 4}], then it’s easy as calling Map.new(list). Having said that, you can also use Map.n…

Today I learnt that for has a reduce option and it’s great ! Thanks :slight_smile:

I tried this code that I never saw: [image] kokolegorille: for [k, v] <- list, reduce: %{} do acc -> Map.put(acc, k, v) end And I have this error: ** (CompileError) iex:3: unsupported option :reduce given to for

Its only available since elixir 1.8. You really should update.

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fuelen February 6, 2020, 7:37am 2

data = [[1, 5], [3, 12], [4, 10]]
Enum.into(data, %{}, fn [a,b] -> {a, b} end)