replacing template pattern with functions in Elixir

template.exs

ExUnit.start

defmodule Grader do
  def grade(grade) do
    cond do
      grade <= 5.0 and grade > 4.0 -> "A"
      grade <= 4.0 and grade > 3.0 -> "B"
      grade <= 3.0 and grade > 2.0 -> "C"
      grade <= 2.0 and grade > 0 -> "D"
      grade == 0 -> "F"
    end
  end
end

defmodule Printer do
  def histogram(grades) do
    grouped = Enum.group_by(grades, fn(grade) -> grade end)
    counts = Enum.map(grouped, fn({k, v}) -> {k, length(v)} end)
  end
end

defmodule Composer do
  def compose(grader, printer) do
    fn(grades) -> Printer.histogram(Enum.map(grades, grader)) end
  end
end

defmodule GradePrintTest do
  use ExUnit.Case
  test "grade and print" do
    g = Composer.compose(&Grader.grade/1, &Printer.histogram/1)
    assert g.([2.3, 4.6, 2.4, 4.5, 1.2, 5.0, 4.9, 4.6, 3.8, 1.7, 4.6, 4.5, 4.4]) == [{"A", 8}, {"B", 1}, {"C", 2}, {"D", 2}]
  end
end