def process_non_terminals(index)
      seq = ""

      index.chop.chars.each do |char|
        seq << char

        if @map.has_key?(seq) && @map[seq]
          fail MiniTermKME, "Ambiguous entry #{index.inspect}"
        end

        @map[seq] = false
      end
    end
def process_non_terminals(index)
      seq = ""

      index.chop.chars.each do |char|
        seq << char

        if @map.has_key?(seq) && @map[seq]
          fail MiniTermKME, "Ambiguous entry #{index.inspect}"
        end

        @map[seq] = false
      end
    end
Handle the preamble characters in the command sequence.