variable-name — a variable name; not evaluated.

accessor-name — a function name; not evaluated.

instance-form — a form; evaluated.

declaration — a declare expression; not evaluated.

forms — an implicit progn.

results — the values returned by the forms.

Creates a lexical environment in which the slots specified by slot-entry are lexically available through their accessors as if they were variables. The macro with-accessors invokes the appropriate accessors to access the slots specified by slot-entry. Both setf and setq can be used to set the value of the slot.

 (defclass thing () 
           ((x :initarg :x :accessor thing-x) 
            (y :initarg :y :accessor thing-y))) 
→ #<STANDARD-CLASS THING 250020173> 
 (defmethod (setf thing-x) :before (new-x (thing thing)) 
   (format t "~&Changing X from ~D to ~D in ~S.~%" 
           (thing-x thing) new-x thing)) 
 (setq thing1 (make-instance 'thing :x 1 :y 2)) → #<THING 43135676> 
 (setq thing2 (make-instance 'thing :x 7 :y 8)) → #<THING 43147374> 
 (with-accessors ((x1 thing-x) (y1 thing-y)) 
                 thing1 
   (with-accessors ((x2 thing-x) (y2 thing-y)) 
                   thing2 
     (list (list x1 (thing-x thing1) y1 (thing-y thing1) 
                 x2 (thing-x thing2) y2 (thing-y thing2)) 
           (setq x1 (+ y1 x2)) 
           (list x1 (thing-x thing1) y1 (thing-y thing1) 
                 x2 (thing-x thing2) y2 (thing-y thing2)) 
           (setf (thing-x thing2) (list x1)) 
           (list x1 (thing-x thing1) y1 (thing-y thing1) 
                 x2 (thing-x thing2) y2 (thing-y thing2))))) 
⊳ Changing X from 1 to 9 in #<THING 43135676>. 
⊳ Changing X from 7 to (9) in #<THING 43147374>. 
→ ((1 1 2 2 7 7 8 8) 
     9 
     (9 9 2 2 7 7 8 8) 
     (9) 
     (9 9 2 2 (9) (9) 8 8))

defclass

The consequences are undefined if any accessor-name is not the name of an accessor for the instance.

with-slots, symbol-macrolet

A with-accessors expression of the form:

expands into the equivalent of

where Q_i is