anchor.diff:  (defstruct (node (:constructor %make-node)
                    (:print-object %print-node))
     sample-indices depth test-attribute test-threshold information-gain 
  -  left-node right-node dtree
  -  leaf-index leaf-weight)
  +  left-node right-node dtree leaf-index)
   
   (defun %print-node (obj stream)
     (format stream "#S(NODE :TEST ~A :GAIN ~A)"
  
positive.code:              (type (simple-array double-float) datamatrix)
               (type (simple-array fixnum) index-offset)
               (type fixnum datum-index n-tree))
      (let ((leaf-index-weight-pairs
              (mapcar/pmapcar
               (lambda (dtree)
                 (let ((node (find-leaf (dtree-root dtree) datamatrix datum-index)))
                   (cons (node-leaf-index node)
                         (node-leaf-weight node))))
               (forest-dtree-list forest))))
        (let ((sv-index (make-array (forest-n-tree forest) :element-type 'fixnum))
              (sv-val (make-array (forest-n-tree forest)
  
negative.code: ;; Delete non-significant nodes
  
  (defun delete-children! (node)
    (setf (node-test-attribute node) nil
          (node-test-threshold node) nil
          (node-left-node node) nil
  