# File truthtable.rb, line 275
  def cnf
    r = []
    @table.each {|inputs, output|
      return output.to_s if inputs.empty?
      next if output
      term = []
      each_input(inputs) {|name, input|
        if input
          term << "!#{name}"
        else
          term << name
        end
      }
      if term.length == 1
        r << term.join('|')
      else
        r << "(#{term.join('|')})"
      end
    }
    return "true" if r.empty?
    r.join(' & ')
  end