def (queue seq)
  (tag queue (list seq lastcons.seq len.seq))

def (enq x q)
  do1 x
    let (l last len) rep.q
      rep.q.2 <- (len + 1)
      if no.l
        rep.q.1 <- (rep.q.0 <- list.x)
        rep.q.1 <- (cdr.last <- list.x)

def (deq q)
  let (l last len) rep.q
    ret ans car.l
      unless zero?.len
        rep.q.2 <- (len - 1)
      rep.q.0 <- cdr.l

def (len q) :case (isa queue q)
  rep.q.2