Syntax:
symbol-function symbol => contents
(setf (symbol-function symbol) new-contents)
Arguments and Values:
symbol---a 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-contents---a 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
Side Effects: None.
Affected By:
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.