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gentemp Symbols Dictionary symbol-name
Accessor

symbol-function

symbol-function symbol ⇒ contents

(setf ( symbol-function symbol) new-contents)

Arguments and Values

symbola symbol.
contents

If the symbol is globally defined as a macro or a special operator, an object of implementation-dependent nature and identity is returned. If the symbol is not globally defined as either a macro or a special operator, and if the symbol is fbound, a function object is returned.

new-contentsa function.

Description

Accesses the symbol’s function cell.

Examples

 (symbol-function 'car) ⇒  #<FUNCTION CAR>
 (symbol-function 'twice) is an error   ;because TWICE isn't defined.
 (defun twice (n) (* n 2)) ⇒  TWICE
 (symbol-function 'twice) ⇒  #<FUNCTION TWICE>
 (list (twice 3)
       (funcall (function twice) 3)
       (funcall (symbol-function 'twice) 3))
⇒  (6 6 6)
 (flet ((twice (x) (list x x)))
   (list (twice 3)
         (funcall (function twice) 3)
         (funcall (symbol-function 'twice) 3)))
⇒  ((3 3) (3 3) 6)   
 (setf (symbol-function 'twice) #'(lambda (x) (list x x)))
⇒  #<FUNCTION anonymous>
 (list (twice 3)
       (funcall (function twice) 3)
       (funcall (symbol-function 'twice) 3))
⇒  ((3 3) (3 3) (3 3))
 (fboundp 'defun) ⇒  true
 (symbol-function 'defun)
⇒  implementation-dependent
 (functionp (symbol-function 'defun))
⇒  implementation-dependent
 (defun symbol-function-or-nil (symbol)
   (if (and (fboundp symbol) 
            (not (macro-function symbol))
            (not (special-operator-p symbol)))
       (symbol-function symbol)
       nil)) ⇒  SYMBOL-FUNCTION-OR-NIL
 (symbol-function-or-nil 'car) ⇒  #<FUNCTION CAR>
 (symbol-function-or-nil 'defun) ⇒  NIL

Affected By

defun

Exceptional Situations

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

Should signal undefined-function if symbol is not fbound and an attempt is made to read its definition. (No such error is signaled on an attempt to write its definition.)

See Also

fboundp, fmakunbound, macro-function,

special-operator-p

Notes

symbol-function cannot access the value of a lexical function name produced by flet or labels; it can access only the global function value.

setf may be used with symbol-function to replace a global function definition when the symbol’s function definition does not represent a special operator. 

(symbol-function symbol) ≡ (fdefinition symbol)

However, fdefinition accepts arguments other than just symbols.

Backlinks

fboundp, fdefinition, Function Call Forms as Places, Function Forms, function, mapc, mapcar, mapcan, mapl, maplist, mapcon, symbol, Symbols Dictionary, Symbols in the COMMON-LISP Package