anchor.diff:  ;;;
   ;;; Machine Learning Building Blocks
   
  +(defun average (array)
  +  (α #'/
  +     (β* #'+ 0 array)
  +     (total-size array)))
  +
   (defun make-random-array (dimensions &key (element-type 't))
     (let ((array (make-array dimensions :element-type element-type)))
       (loop for index below (array-total-size array) do
  
positive.code:          (upper-bounds (make-array k :initial-element 0))
           (filters
             (make-trainable-parameter
              (make-random-array n-filters :element-type (element-type array))))
           (d nil))
      ;; Determine the dimension of the stencil.
      (loop for offsets in stencil do
  
negative.code:               for value in (multiple-value-list
                              (apply #'call-network training-network (reverse args)))
                do (setf (trainable-parameter-value trainable-parameter)
                         value))))
      ;; Return the trained network.
      network))
  
  (defun nth-datum (index data)
    (reshape
  