declare
fun {NewQueue}
   X C={NewCell q(0 X X)}
   proc {Insert X}
   N S E1 N1 in
      {Exchange C q(N S X|E1) q(N1 S E1)}
      N1=N+1
   end
   fun {Delete}
   N S1 E N1 X in
      {Exchange C q(N X|S1 E) q(N1 S1 E)}
      N1=N-1
      X
   end
in
   queue(insert:Insert delete:Delete)
end