declare
fun {NewQueue}
   ...
   fun {Size}
      lock L then @C.1 end
   end
   fun {DeleteAll}
      lock L then
      X q(_ S E)=@C in
         C:=q(0 X X)
         E=nil S
      end
   end
   fun {DeleteNonBlock}
      lock L then
         if {Size}>0 then [{Delete}] else nil end
      end
   end
in
   queue(insert:Insert delete:Delete size:Size
         deleteAll:DeleteAll deleteNonBlock:DeleteNonBlock)
end