anchor.diff:    (:metaclass funcallable-standard-class)
     (:documentation
      "A transformation is an analytically tractable function from indices to
  -   indices."))
  +    indices."))
   
   (define-class operator-metadata ()
     ((result-type :type type-specifier)
  
positive.code:    (refcount     :type non-negative-fixnum :initform 0 :accessor refcount))
    (:documentation
     "A data structure of dimension D is a mapping from elements of
     INDEX-SPACE to values of type ELEMENT-TYPE.
  
     INPUTS is a list of data structures on which the definition of this data
     structure depends on.
  
     REFCOUNT is an implementation detail. For ordinary data structures it
     tracks how many times the data structure appears as an input of another
     data structure. For immediate data structures, it tracks how many times
     the data structure appears as the source of a kernel."))
  
  (defmethod initialize-instance :after ; reference counting
      ((instance data-structure) &key &allow-other-keys)
  
negative.code: (define-class virtual-machine () ()
    (:documentation
     "A virtual machine is an abstraction over a set of hardware
      resources. All handling of kernels --- such as performance analysis,
      compilation and execution --- is done in the context of a particular
      virtual machine."))
  
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  ;;;
  