CLHS: Accessor SYMBOL-VALUE

#

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.)

See Also:

boundp, makunbound, set, setq

Notes:

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

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