declare
fun {NewPrioQueue}
   Q={NewCell nil}
   proc {Enqueue X Prio}
      fun {InsertLoop L}
         case L of pair(Y P)|L2 then
            if Prio<P then pair(X Prio)|L
            else pair(Y P)|{InsertLoop L2} end
         [] nil then [pair(X Prio)] end
      end
   in Q:={InsertLoop @Q} end

   fun {Dequeue}
      pair(Y _)|L2=@Q
   in
      Q:=L2 Y
   end

   fun {Delete Prio}
      fun {DeleteLoop L}
         case L of pair(Y P)|L2 then
            if P==Prio then X=Y L2
            else pair(Y P)|{DeleteLoop L2} end
         [] nil then nil end
      end X
   in Q:={DeleteLoop @Q} X end

   fun {IsEmpty} @Q==nil end
in
   queue(enqueue:Enqueue dequeue:Dequeue
         delete:Delete isEmpty:IsEmpty)
end