anchor.diff:  
   ;;; Retrieval
   
  -(defun find-seq (trie seq)
  -  "Find a sequence from trie"
  +(defun obtain-seq (trie seq)
  +  "Get a sequence from trie by following the keys in the sequence."
     (when (zerop (length seq))
  -    (return-from find-seq trie))
  +    (return-from obtain-seq trie))
     (let ((symbol (find-key trie (elt seq 0))))
       (when symbol
  -      (find-seq symbol (subseq seq 1)))))
  +      (obtain-seq symbol (subseq seq 1)))))
   
   (defun find-key (trie key)
  -  "Return a symbol matching key from trie's branches."
  +  "Get a symbol matching key from trie's branches."
     (find key (trie-branches trie) :test #'equal :key #'trie-key))
   
   (defun sym-interval (trie key)
  
positive.code: 
  (defun trie-prob (root suffix)
    "Returns probability of suffix on given trie."
    (let ((node (find-seq root suffix)))
      (when node
        (/ (trie-width node) (trie-width root)))))
  
  
negative.code: 
  ; (defun remove-seq (trie seq &optional (count 1))
  ;   "### Remove a sequence from trie"
  ;   (unless (obtain-seq trie seq)
  ;     (return-from remove-seq nil))
  ;   (decf (trie-width trie) (max count 1))
  ;   (when (zerop (length seq))
  