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ANSI Common Lisp  10 Symbols 10.2 Dictionary of Symbols
| 10.2.14 symbol-value |
Accessor |
- 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
- Affected By:
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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:
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boundp, makunbound, set, setq
- Notes:
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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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None.
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