mapper.ex

defmodule Mapper do
 
  def map([], _func), do: []
  def map([head|tail], func) do
    [func.(head) | map(tail, func)]
  end
 
  def mapsum([], _func), do: 0
  def mapsum([head|tail], func) do
    func.(head) + mapsum(tail, func)
  end
 
  def max([]), do: 0
  def max([head|tail]) do
    if head > max(tail), do: head, else: max(tail)
  end
 
  def span(from, to) do
    if from <= to, do: [from | span(from + 1, to)], else: []
  end
 
end
 
ExUnit.start
 
defmodule TestMapper do
  use ExUnit.Case
 
  test "iterate a list and apply a function that adds 1" do
    assert Mapper.map([1,2,3], &1 + 1) == [2,3,4]
  end
 
  test "iterate a list and apply a function that doubles" do
    assert Mapper.map([1,2,3], fn(x) -> x*2 end) == [2,4,6]
  end
 
  test "iterate a list and apply a funciton to square" do
    assert Mapper.map([1,2,3], fn(x) -> x*x end) == [1,4,9]
  end
 
  test "iterate a list and apply an addition function then sum" do
    assert Mapper.mapsum([1,2,3], &1 + &1) == 12
  end
 
  test "iterate a list and apply a multiplication function then sum" do
    assert Mapper.mapsum([1,2,3], fn(n) -> n*n end) == 14
  end
 
  # you can also pass atoms to test
  test :max_in_list do
    assert Mapper.max([4,8,5,7,3]) == 8
  end
 
  test :span_a_valid_range do
    assert Mapper.span(1, 5) == [1,2,3,4,5]
  end
 
end