convert.ex

defmodule Math do

    def pow( num, power ) do
      _pow num, power, 1
    end

    def _pow( num, 0, acc ) do
      acc
    end

    def _pow( num, power, acc ) when power > 0 do
      _pow( num, power - 1, acc * num)
    end
  
end

defmodule Convert do

  defmodule Binary do

    import Enum
    import Math


    def to( value ) when value > 0 do
      _to value, []
    end

    def _to( 0, list ) do
      list
    end

    def _to( value, list ) when value > 0 do
      _to div(value, 2), [ rem(value, 2) | list ]
    end

    def from( value ) when is_list( value ) do
      _from Enum.reverse( value ), 0, 0
    end

    def _from( [], power, acc ) do
      acc
    end


    def _from( [ v | tail ], power, acc ) do
      _from tail, power + 1, acc + ( v * pow(2, power) )
    end

  end

end