    # File lib/graphviz.rb, line 690
      def self.default( hOpts )
        hOpts.each do |k, v|
          case k.to_s
            when "use"
              @@prog = v
            when "path"
              @@path = v.split( "," ).map{ |x| x.strip }
            when "errors"
              @@errors = v
            when "extlibs"
              @@extlibs = v.split( "," ).map{ |x| x.strip }
            when "output"
              warn ":output option is deprecated!"
              @@format = v
            else
              warn "Invalide option #{k}!"
          end
        end
      end