# File truthtable.rb, line 194
  def dnf
    r = []
    @table.each {|inputs, output|
      next if !output
      term = []
      each_input(inputs) {|name, input|
        if input
          term << name
        else
          term << "!#{name}"
        end
      }
      r << term.join('&')
    }
    r.join(' | ')
  end