declare
proc {DFS T}
   fun {TreeInsert S T}
      if T\=leaf then T|S else S end
   end

   proc {DFSStack S1}
      case S1
      of nil then skip
      [] X|S2 then
         tree(Key Val L R)=X
      in
         {Browse Key#Val}
         {DFSStack {TreeInsert {TreeInsert S2 R} L}}
      end
   end
in
   {DFSStack {TreeInsert nil T}}
end