anchor.diff:  ;;;
   ;;; We have tested this implementation on randomly generated graphs by
   ;;; comparing it to the result of a trivial algorithm for computing
  -;;; dominators (see below).
  +;;; dominators (see the file test-dominance.lisp).
  +;;;
  +;;; The result is returned as an EQ hash table where the keys
  +;;; represent each node in the graph, and the value associated with
  +;;; the key is the immediate dominator of the node that is the key.
  +;;;
  +;;; The name of this function is not exported, because there is no
  +;;; reason for client code to use it directly.  It is used as a
  +;;; subroutine for computing the dominance tree and the dominance
  +;;; frontiers.
   
   (defun immediate-dominators (start-node successor-fun)
     (let* ((pred (make-hash-table :test #'eq))
  
positive.code: ;;;
  ;;; Compute the immediate dominator of each node in an arbitrary
  ;;; flowgraph.
  ;;;
  ;;; This function is a very close implementation of the algorithm by
  ;;; Thomas Lengauer and Robert Endre Tarjan, as described in their
  ;;; paper "A Fast Algorithm for Finding Dominators in a Flowgraph",
  
negative.code: ;;;
  ;;; Dominance frontiers.
  
  ;;; Compute a hash table that maps every node in a dominance tree to a
  ;;; list of its children in that tree.
  (defun children (dominance-tree)
    (let ((result (make-hash-table :test #'eq)))
      (loop for node being each hash-key of dominance-tree
  