qsort.exs

defmodule Htest do
  def equals(message, expect, value) do
    IO.puts "#{message}:  #{expect == value} "
  end
end

defmodule Qsort do
 
  def qsort([]), do: []                                #base case for qsort 
  def qsort([pivot|[]]), do: [pivot]                   #base case for qsort 
  def qsort([pivot|tail]) do                           #how to get head and tail from 
    lower = Enum.filter(tail, fn(n) -> n < pivot  end) #How to filter
    higher = Enum.filter(tail, fn(n) -> n > pivot  end)

  qsort(lower) ++  [pivot] ++ qsort(higher) 
  end
end

# Test setup 
list = [ 6, 1, 3, 5, 9, 8, 4, 7, 2]

result = Qsort.qsort list
expected = [1, 2, 3, 4, 5, 6, 7, 8, 9]

# learned how to inspect in elixir
# IO.inspect result

IO.puts "testing" 
Htest.equals "the list is sorted", expected, result
IO.inspect result