anchor.diff:  ;; Function to get the root of a tree
   (defun get-root()
     (make-tree-node :data (make-node-data :score 0.0 :game-number 0 :lower-bound 0.0 :upper-bound 1.0)))
  -
  -;; Gets the root of the tree for the current node based on its ancestors
  -;; Incorrect function. Doesn't work :(
  -(defun find-root(node)
  -  (if(eq (tree-node-parent node) nil)
  -     node
  -     (find-root (tree-node-parent node))))
   
   ;; Function to initialize the sensory channels for the agent
   (defun init-sensory-channels()
  
positive.code:     (setf (node-data-score (tree-node-data tr)) (+ (node-data-score (tree-node-data tr)) 1))))
  
  ;; Based on the scene and the feature-detectors provided, 
  ;; filters the list of feature-detectors based on the scene and an existing saliency treshold
  ;; Def: Saliency is the smallest of the absolute values
  ;; of the distance between the topic and any other object
  (defun salient-feature-detectors(feature-detectors scene)
    "Saliency filter for feature detectors given a treshold"
    (let ((filtered-fds '()))
      (loop for fd in feature-detectors do
           (let ((abs-distances '()) (topic-value (get-input-object-value (scene-topic scene) (sensory-channel-feature-name fd))))
             (loop for o in (scene-objects scene) do
                  (let ((obj-value (get-input-object-value o (sensory-channel-feature-name fd))))
                    (setq abs-distances (append abs-distances (list (abs (- topic-value obj-value)))))))
             (when (> (apply 'min abs-distances) *saliency-treshold*)
               (setq filtered-fds (append filtered-fds (list fd))))))
      filtered-fds))
  
  
negative.code:   "Gets the age of a node"
    (- *current-game* (node-birth-game node)))
  
  ;; Executes a prunning in a tree
  ;; Function doesn't work properly
  (defun tree-pruning(tree)
    "Pruning depending on the age and score of the nodes"
    (let ((score (node-score tree)) (age (node-age tree)))
      (if(and (> age *pruning-min-age*) (< (/ score age) *pruning-threshold*))
         (progn 
          ;;(format t "EXECUTING PRUNING")
           (setf (tree-node-left-child tree) nil)
           (setf (tree-node-right-child tree) nil))
         (when (and 
  