Elixir program, to find the most frequently occurring alpha numeric in a very large datafile.

alpha_max.ex

defmodule AlphaMaxPar do
  def count_alpha(string) do
    string
    |> String.codepoints
    |> Enum.filter(fn c -> c =~ ~r/[A-Za-z0-9]/ end)
    |> Enum.reduce(Map.new, fn c,acc -> Map.update(acc, c, 1, &(&1+1)) end)
  end
end

File.stream!("2019-annual/taxa.txt", [encoding: :utf8], 1_000_000)
|> Task.async_stream(&AlphaMaxPar.count_alpha/1, max_concurrency: 6, ordered: false)
|> Enum.map(fn {:ok, x} -> x end)
|> Enum.reduce(fn a, b -> Map.merge(a, b, fn _k, v1, v2 -> v1 + v2 end) end)
|> Enum.sort_by(fn {_k,v} -> -v end)
|> Enum.fetch!(0)
|> IO.inspect