anchor.diff:                       :trans-hash (value :trans-hash)
                        :account-number (value :account-number)
                        :account-type (value :account-type)
  -                     :message-code (cdr (assoc :code message))
  -                     :message-description (cdr (assoc :description message))
  -                     :error-code (cdr (assoc :error-code err))
  -                     :error-text (cdr (assoc :error-text err))))))
  +                     :message-code (or (cdr (assoc :code message)) "")
  +                     :message-description (or (cdr (assoc :description message)))
  +                     :error-code (or (cdr (assoc :error-code err)) "")
  +                     :error-text (or (cdr (assoc :error-text err)) "")))))
   
   (defun execute (request endpoint)
     (check-type request request)
  
positive.code: 
  (defgeneric transaction-response-response-code (transaction-response))
  
  (defconstant +transaction-response-code-approved+ 1)
  (defconstant +transaction-response-code-declined+ 2)
  (defconstant +transaction-response-code-error+ 3)
  (defconstant +transaction-response-code-held-for-review+ 4)
  
  (defun transaction-response-response-code-description (transaction-response)
    (ecase (transaction-response-response-code transaction-response)
      (+transaction-response-code-approved+ :approved)
      (+transaction-response-code-declined+ :declined)
      (+transaction-response-code-error+ :error)
      (+transaction-response-code-held-for-review+ :held-for-review)))
  
  (defclass auth-capture-transaction-response (transaction-response)
    ((response-code :initarg :response-code :reader transaction-response-response-code)
  
negative.code:    ;; LATER other fields...
     )
    (:default-initargs
     :response-code ""
      :auth-code ""
      :avs-result-code ""
      :cvv-result-code ""
      :cavv-result-code ""
      :trans-id ""
      :ref-trans-id ""
      :trans-hash ""
      :account-number ""
      :account-type ""
      :message-code ""
      :message-description ""
      :error-code ""
      :error-text ""))
  
  ;; TODO refun-transaction-response
  ;; TODO void-transaction-response
  