# File warshall.rb, line 262
        def komp(rel) 
          erg=Relation.new([[]]) 
          erg.basis!(@basis+rel.basis) 
               erg.each{|i| erg.nach[i]=Menge.new([]); erg.vor[i]=Menge.new([])} 
               erg.each{|i| @nach[i].each{|j| erg.nach[i]+=rel.nachfolger(j)}if @nach[i]!=nil} 
               erg.each{|i| rel.vor[i].each{|j| erg.vor[i]+=vorgaenger(j)}if rel.vor[i]!=nil} 
               return erg 
     end