(defmacro copy-expression (comb)
  `(let ((exp (expressions ,comb))
	 (cell (cons nil nil)))
     (let ((new (append exp cell)))
       (rplaca cell new)
       new)))

(defmacro first-expression (argl-exp)
  `(car ,argl-exp))

(defmacro rest-expressions (argl-exp)
  `(cdr ,argl-exp))

(defmacro last-expression? (argl-exp)
  `(null (cdr (cdr ,argl-exp))))

(defmacro set-current-argument (argl-exp val)
  `(rplaca ,argl-exp ,val))

(defmacro uncircularize (argl-exp)
  `(assign argl (car ,argl-exp)))