defmodule CPUtils do
  #
  # "System" functions.
  #

  @doc """
  timeit(fun)

  From https://stackoverflow.com/questions/29668635/how-can-we-easily-time-function-calls-in-elixir

  A more elaborate timing function. Prints
  * Name of the function
  * Result
  * Time in seconds

  ##Examples##

       > timeit(&test1/0)

  """
  def timeit(fun) do
    # Convert the function (e.g. &Euler1.euler1a/0 to a string
    fun_s = Kernel.inspect(fun)
    {time0, res} = :timer.tc(fun, [])
    time = (time0 / 1_000_000) |> :erlang.float_to_binary([:compact, decimals: 5])
    IO.puts("#{fun_s} res:#{res} time:#{time}s")
  end

  @doc """
  timeit_simple(fun)

  A simple timing function, returns the time in seconds (as a string).

  ##Examples##

       > Util.timeit_simple(&Test1.main/0)

       > Util.timeit_simple(fn () -> Test1.main() end)

  """
  def timeit_simple(fun) do
    {time0, res} = :timer.tc(fun, [])
    IO.inspect(res)
    (time0 / 1_000_000) |> :erlang.float_to_binary([:compact, decimals: 5])
  end

  @doc """
  mat_at(m,i,j)

  Returns the value (`i`,`j`) of the 2d matrix `mat`.

  ##Examples##

       iex> [[1,2,3],[4,5,6],[7,8,9]] |> mat_at(1,2)
       6
  """
  def mat_at(m, i, j) do
    m |> Enum.at(i) |> Enum.at(j)
  end

  @doc """
  transpose(m)

  Returns a transposed version of `m`.

  ##Example##

       iex> [[1,2,3],[4,5,6],[7,8,9]] |> transpose
       [[1, 4, 7], [2, 5, 8], [3, 6, 9]]
  """
  def transpose(m) do
    Enum.zip_with(m, &Function.identity/1)
  end
end