# Pastebin Qq2cyT4v
(defmacro with-cpring6 ((cpinternals cpindex) &body body)
  "Expose two SETF-able symbol-macros inside BODY:
     @6q     ⇔ (aref CPINTERNALS CPINDEX)
     @6theta ⇔ (aref CPINTERNALS (+ 1 CPINDEX)
     @6phi   ⇔ (aref CPINTERNALS (+ 2 CPINDEX))"
  (let ((vec (gensym "VEC-"))
        (idx (gensym "IDX-")))
    `(let ((,vec ,cpinternals)
           (,idx ,cpindex))
       (symbol-macrolet ((@6q     (aref ,vec ,idx))
                         (@6theta (aref ,vec (+ 1 ,idx)))
                         (@6phi   (aref ,vec (+ 2 ,idx)))
                         )
                  ,@body))))

;;; The old way of extracting the parameters
(defun extract-ring6-cps-old (cpinternals cpindex)
  (values (aref cpinternals cpindex)         ; q
          (aref cpinternals (+ 1 cpindex))   ; theta
          (aref cpinternals (+ 2 cpindex)))) ; phi

;;; The more readable and more future proof
(defun extract-ring6-cps (cpinternals cpindex)
  (with-cpring6 (cpinternals cpindex)
    (values @6q @6theta @6phi)))