anchor.diff:  
   ;;; Insertion
   
  -(defun add-seqs (trie seqs)
  -  (mapcar #'(lambda (seq) (add-seq trie seq)) seqs))
  -
  -(defun add-seq (trie seq &optional (count 1))
  +(defun trie-add-seqs (trie seqs)
  +  (mapcar #'(lambda (seq) (trie-add-seq trie seq)) seqs))
  +
  +(defun trie-add-seq (trie seq &optional (count 1))
     "Add a branch to the trie count times. Modifies trie in-place.
     If branch already exists, increase it’s width.
     A count below one is changed to one."
  
positive.code: ;;; -*- Mode: Lisp; Syntax: Common-Lisp; Package: ptrie -*-
  ;;;
  ;;; -------------------------------------------------------------------------
  ;;; P-TRIE - probability trie (with branch widths)
  ;;; -------------------------------------------------------------------------
  ;;;
  ;;; Author:
  ;;;   Peter Hillerström
  ;;; Version:
  ;;;   0.2
  ;;; Initial Common Lisp version:
  ;;;   2010-08-01
  ;;; 
  ;;; Features:
  ;;; 
  
negative.code: ;;;   More information about tries:
  ;;;   http://en.wikipedia.org/wiki/Trie
  ;;;
  
  (in-package #:twist)
  
  (setq *print-pretty* t)
  (setq *print-circle* t)
  