anchor.diff:          (subseq seq 0 (max 0 (+ (length seq) n)))
           (subseq seq (min (length seq) n)))))
   
  +(-> take-while (function sequence) sequence)
   (defsubst take-while (pred seq)
     "Return the prefix of SEQ for which PRED returns true."
     (seq-dispatch seq
       (ldiff seq (member-if-not pred seq))
       (subseq seq 0 (position-if-not pred seq))))
   
  +(-> drop-while (function sequence) sequence)
   (defsubst drop-while (pred seq)
     "Return the largest possible suffix of SEQ for which PRED returns
   false when called on the first element."
  
positive.code:                (return)))
           seqs)))))
  
  (defun of-length (length)
    "Return a predicate that returns T when called on a sequence of
  length LENGTH.
  
negative.code:         ((< (length x) (length y)) y)
          (t x)))
  
  (-> longest (sequence) sequence)
  (defun longest (seqs)
    "Return the longest seq in SEQS."
    (reduce #'longer seqs))
  
  (-> shortest (sequence) sequence)
  (defun shortest (seqs)
    "Return the shortest seq in SEQS."
    (reduce (lambda (x y)
  