lists.ex

lists.ex

defmodule Lists do

  def len([]), do: 0
  def len([_h|t]), do: 1 + len(t)

  def sum([]), do: 0
  def sum([h|t]), do: h + sum(t)

  def double([]), do: []
  def double([h|t]), do: [ 2*h | double(t) ]

  def square([]), do: []
  def square([h|t]), do: [ h*h | square(t) ]

  def map([], _func), do: []
  def map([h|t], func) do
    [func.(h) | map(t, func)]
  end

  def sum_pairs([]), do: []
  def sum_pairs([ h1, h2 | t]), do: [ h1 + h2 | sum_pairs(t) ]

end