Hello, guys!

I was doing some exercises from exercism.io and in some moment a needed to update a Map, I did and finished the exercise. After a while, I found the function Enum.frequencies/1 that could have helped me on the exercise. I decided open Elixir source code to see implementation of Enum.frequencies/1 that is this:

  @doc since: "1.10.0"
  @spec frequencies(t) :: map
  def frequencies(enumerable) do
    reduce(enumerable, %{}, fn key, acc ->
      case acc do
        %{^key => value} -> %{acc | key => value + 1}
        %{} -> Map.put(acc, key, 1)
      end
    end)
  end

Then, the question came to me: There’s any difference between map.put/3 and the built in Map update %{map | “key” => “value”}?

I write my version of Enum.frequencies/1 using Enum.reduce/3, and I replaced %{^key => value} -> %{acc | key => value + 1} by %{^x => value} -> Map.put(acc, x, value + 1) and did work.
I would like to know if there is any reason for Elixir source code to use this syntax %{acc | key => value + 1} on Enum.frequencies/1