defmodule RL do
  @moduledoc """
  Some simple linked list printers
  RL for Recursive List
  author: gtowell
  Created: July, 2022
  """

  @doc """
  Print the contents of a list recursively
  but in a very imperative way using a simple recursive function and a base case in an if statement
  """
  def prnt_lst(lst) do
    if lst==[] do
      # nothing
    else
      IO.puts(hd(lst))
      # tl is a built in function to get the "tail" of a list
      prnt_lst(tl(lst))
    end
  end

  @doc """
  Print the contents of a list. Consists of two functions.
  First, Handler for the empty list when printing a list
  Second when the list is NOT empty
  Often order of appearance of matching functions is importance because if two can match, the first one wins
  In this case, not as important
  """
  def matchPrnt_lst([]) do
    IO.puts "done"
  end

 def matchPrnt_lst([h | r]) do
    IO.puts h
    matchPrnt_lst(r)
  end

  @doc """
  A function to print numbers in an arithmetic sequence. This illustrates the
  use of a guard clause.   In this case, the order of the two functions
  is important because the second will always match everything
  """
  def to_lim_by_m_from_s(lim, m, s) when s<lim do
    IO.puts s
    to_lim_by_m_from_s(lim, m, s+m)
  end
  def to_lim_by_m_from_s(_,_,_) do
    IO.puts "thats all folks"
  end

  @doc """
  Examples
  """
  def main do
    aa = [0,1,2,3,4,5,6,7,8,9]
    prnt_lst(aa)
    matchPrnt_lst(aa)
    to_lim_by_m_from_s(46,7,0)
  end
end


defmodule ZeroTen do
  @moduledoc """
  Contains two very small programs for collecting the number of 0 to 10 into a list
  Created Oct 24, 2020 gtowell
  """

  @doc """
  NOt tail recursive version of the task.
  """
  def zt(10) do
    []
  end
  def zt(i) do
    [i | zt(i+1)]
  end

  @doc """
  Tail recursive version of the task.
  Note that this returns the list in descending order and that is requires an additional parameter to pass along the accumulating answer.
  """
  def ztt(10, res) do
    res
  end
  def ztt(i, res) do
    ztt(i+1, [i|res])
  end

end

IO.inspect ZeroTen.ztt(0,[])

#RL.main