Stak_Queue.oz~

declare
class Stack
   attr SL
   meth init
      SL := {NewCell nil}
   end
   meth size($)
      {Length @SL}
   end
   meth isEmpty($)
      @SL==nil
   end
   meth top($)
      case @SL
      of H|T then H
      else raise emptyStack end
      end
   end
   meth pop($)
      case @SL
      of H|T then
	 SL := T
	 H
      else raise emptyStack end
      end
   end
   meth push(X)
      SL := X|@SL
   end
end
class Queue
   attr QL
   meth init
      QL := {NewCell nil}
   end
   meth size($)
      {Length @QL}
   end
   meth isEmpty($)
      @QL==nil
   end
   meth front($)
      case @SL
      of H|T then H
      else raise emptyQueue end
      end
   end
   meth dequeue($)
      case @QL
      of H|T then
	 QL := T
	 H
      else raise emptyQueue end
      end
   end
   meth enqueue(X)
      QL := {Reverse X|{Reverse @SL}}
   end
end

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