csv.ex

defmodule Coercer do
  @date_format "{YYYY}-{0M}-{0D}"

  def coerce({value, idx}) do
    case idx do
      1 -> Decimal.new(value)
      2 -> Timex.parse(value, @date_format) |> elem(1)
      _ -> value
    end
  end
end

records = File.stream!("input.csv")
|> CSV.decode
|> Enum.drop(1)
|> Enum.map(fn row ->
  Stream.with_index(row)
  |> Enum.map(fn cell ->
    Coercer.coerce(cell)
  end)
end)

IO.inspect records

defmodule DecSum do
  def sum(enum) do
    enum |> Enum.reduce(Decimal.new(0), &Decimal.add/2)
  end
end

vals = Enum.map(records, fn(row) ->
  Enum.fetch!(row, 1)
end)

IO.inspect DecSum.sum(vals)