[LISPWORKS][Common Lisp HyperSpec (TM)] [Previous][Up][Next]

Accessor SYMBOL-VALUE

Syntax:

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.

Description:

Accesses the symbol's value cell.

Examples:

 (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

Side Effects: None.

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.)

Notes:

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