Problem with access of slots in Lisp (CLOS) -

I have a node class that has an 'element' slot that contains a list with numbers and one letter, for example For:

'(1 2 3 b 4 5 6)

  (defclass node ((element: reader get-element: author set-element : Initform '(): Initag: Element: Documentation "Element"))   
 
 Part of the program is considered to take' Element 'slot, swap one of the letters with Swap list as the number and finally a new node object as its 'element' slot I already have a swap function that receives a list and two members of that list and swaps them using rotatable functions. 
 
 To check that Swap functions was working I have made the following part of the code that stores the element in a temporary variable and swaps the letter 'B' with a number in the list: 
 
 
 < Code> (setf root (make-instance 'node)) (Set-element '(1 2 3B 4 5 6 7 8) root)  
 (setf temp (get-element root)) (swap temp' b 4)   
 
 The problem is that the 'element' slot root object is temporarily swap temporarily strange I tried to change the swap function to reverse and none of the two modifies it . 
 
 I do not know in any way that a slot can give a path to any variable or to stop the above events. 
 
 Thank you. 
 
 
 
 
 
  reverse  and gives a new list  Rotatef < / Code> (like  setf ,  incf  and so on) modify a location. You must do  copy-list  or  copy-tree  your  element  to create a new list, which you will then modify.