anchor.diff:     (shock :accessor shock :type boolean :initform nil))
     (:documentation "Describes a standard multilayer, fully-connected backpropagation neural network."))
   
  -(defmethod initialize-instance :after ((neuron t-neuron) &key)
  -  (setf (id neuron) (incf (next-id (net neuron)))))
  -
   (defmethod output-layer ((net t-net))
     (car (last (layers net))))
   
  
positive.code:                (error ":layer-type required") :type keyword)
     (neuron-count :accessor neuron-count :initarg :neuron-count
                   :initform (error ":neuron-count required") :type integer)
     (net :reader net :initarg :net :initform (error ":net required")
          :type t-net)) 
    (:documentation "Describes a neural network layer."))
  
  (defmethod initialize-instance :after ((layer t-layer) &key)
    (let ((size (+ (neuron-count layer)
                   (if (equal (layer-type layer) :hidden) 1 0))))
      (setf (neuron-count layer) size)
      (setf (neuron-array layer)
            (make-array size :element-type 't-neuron :fill-pointer 0))
  
negative.code:   net)
  
  (defmethod initialize-instance :after ((net t-net) &key)
    (setf (layers net)
          (loop for layer-spec in (topology net)
             for layer-index = 0 then (1+ layer-index)
  