def encoding_for_interleaved(*bars_and_spaces)
      bar = false#starts with bar
      bars_and_spaces.flatten.inject '' do |enc,bar_or_space|
        bar = !bar
        enc << (bar ? '1' : '0') * (bar_or_space == WIDE ? wide_width : narrow_width)
      end
    end
def encoding_for_interleaved(*bars_and_spaces)
      bar = false#starts with bar
      bars_and_spaces.flatten.inject '' do |enc,bar_or_space|
        bar = !bar
        enc << (bar ? '1' : '0') * (bar_or_space == WIDE ? wide_width : narrow_width)
      end
    end
Encodes an array of interleaved W or N bars and spaces
ex: [W,N,W,W,N,N] => "111011100010"