# Pastebin aXK1SAG2
(defmacro with-cpring5 ((vec idx &optional suffix) &body body)
  "Inside BODY expose two SETF-able symbol-macros:

      @5q[-SUFFIX]   ≡ (aref VEC IDX)
      @5phi[-SUFFIX] ≡ (aref VEC (1+ IDX))

Supply SUFFIX (a symbol or string) when you need distinct names
while nesting several WITH-CPRING5 forms."
  (let* ((pkg *package*)
         (tail  (if suffix (format nil "-~A" suffix) ""))
         (qsym  (intern (concatenate 'string "@5Q"  tail)  pkg))
         (psym  (intern (concatenate 'string "@5PHI" tail) pkg))
         (v     (gensym "VEC-"))
         (i     (gensym "IDX-")))
    `(let ((,v ,vec)
           (,i ,idx))
       (symbol-macrolet ((,qsym  (aref ,v ,i))
                         (,psym  (aref ,v (1+ ,i))))
         ,@body))))


(let ((v (make-array 10 :element-type 'double-float :initial-element 0d0)))
  (with-cpring5 (v 2 outer)
    (with-cpring5 (v 4 inner)
      (setf @5q-outer 1d0   @5phi-outer 2d0   ; v[2], v[3]
            @5q-inner 3d0   @5phi-inner 4d0)  ; v[4], v[5]
      (+ @5q-outer @5phi-outer @5q-inner @5phi-inner))))
;; ⇒ 10.0d0