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symbol-value symbol ⇒ value
(setf ( symbol-value symbol) new-value)
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
makunbound, set, setq
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.)
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.