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  ANSI Common Lisp   10 Symbols   10.2 Dictionary of Symbols

10.2.14 symbol-value Accessor

symbol-value symbol    value

(setf (symbol-value symbol) new-value)

Arguments and Values:
symbol - a symbol that must have a value.

value, new-value - an object.

Accesses the symbol's value cell.

 (setf (symbol-value 'a) 1)  1
 (symbol-value 'a)  1
 ;; SYMBOL-VALUE cannot see lexical variables.
 (let ((a 2)) (symbol-value 'a))  1
 (let ((a 2)) (setq a 3) (symbol-value 'a))  1
 ;; SYMBOL-VALUE can see dynamic variables.
 (let ((a 2)) 
   (declare (special a)) 
   (symbol-value 'a))  2
 (let ((a 2)) 
   (declare (special a)) 
   (setq a 3)
   (symbol-value 'a))  3
 (let ((a 2))
   (setf (symbol-value 'a) 3)
   a)  2
 a  3
 (symbol-value 'a)  3
 (let ((a 4))
   (declare (special a))
   (let ((b (symbol-value 'a)))
     (setf (symbol-value 'a) 5)
     (values a b)))  5, 4
 a  3
 (symbol-value :any-keyword)  :ANY-KEYWORD
 (symbol-value 'nil)   NIL
 (symbol-value '())   NIL
 ;; The precision of this next one is implementation-dependent.
 (symbol-value 'pi)  3.141592653589793d0  

Affected By:
makunbound, set, setq

Exceptional Situations:
Should signal an error of type type-error if symbol is not a symbol.

Should signal unbound-variable if symbol is unbound and an attempt is made to read its value. (No such error is signaled on an attempt to write its value.)

See Also:
boundp, makunbound, set, setq

symbol-value can be used to get the value of a constant variable. symbol-value cannot access the value of a lexical variable.

Allegro CL Implementation Details:

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