defmodule FunMatch do
  @moduledoc """
  Parameter matching for functions.
  Note that the oder in which functions are defined in a module
  matters.  Matching is to the first found in order rather than to the
  "most specific" match.  This is likely because "most specific" may be
  ill-defined -- ie, which is preferred when 2 of 3 match in two different ways.
  Author: gtowell
  Created: July 2022
  """

  @doc """
  matching with 3 numeric parameters.   Just take the first match
  so 1,1,1 will never be used
  """
  def tst(0,0,0) do
    IO.puts "all zero"
  end
  def tst(2,_,_) do
    IO.puts "2 first"
  end
  def tst(a,b,c) do
    IO.puts "none match"
  end
  def tst(1,1,1) do
    IO.puts "all ones"
  end

  @doc """
  matching with one list.   Empty list can be last as it will not match
  to [h|r] or [a].  However a list with one item will match to
  [h|r] (h gets the item, r gets []) so in this ordering the fun with [a]
  will never get called.
  """
  def rl([h|r]) do
    IO.puts "big list"
  end
  def rl([a]) do
    IO.puts "one item list"
  end
  def rl([]) do
    IO.puts "empty list"
  end

  def main() do
    tst(0,0,0)
    tst(1,1,1)
    tst(2,5,9)
    tst(42,5,8)

    rl([1,2,3])
    rl([2])
    rl([])

  end
end


FunMatch.main