Geodistance (havenshine function) in elixir

havershine.ex

defmodule Havershine do
  def distance(lng1, lat1, lng2, lat2) do
    [rLng1, rLat1, rLng2, rLat2] = for deg <- [lng1, lat1, lng2, lat2], do: deg2rad(deg)

    dLon = rLng2 - rLng1
    dLat = rLat2 - rLat1

    a = :math.pow(:math.sin(dLat/2), 2) + :math.cos(rLat1) * :math.cos(rLat2) * :math.pow(:math.sin(dLon/2), 2)

    c = 2 * :math.asin(:math.sqrt(a))

    km = 6372.8 * c
  end

  defp deg2rad(deg), do: :math.pi()*deg/180
end