Function fboundp

Syntax:

Pronunciation:

[ˌefˈba.undpē]

Arguments and Values:

name—a function name.

generalized-boolean—a generalized boolean.

Description:

7.1.1 20Returns true if name is fbound; otherwise, returns false.

Examples:

Some "implementation dependent" => "true" per Moore #2 (first public review). -kmp 12-May-93

 (fboundp 'car) → true
 (fboundp 'nth-value) → false
 (fboundp 'with-open-file) → true
 (fboundp 'unwind-protect) → true
 (defun my-function (x) x) → MY-FUNCTION
 (fboundp 'my-function) → true
 (let ((saved-definition (symbol-function 'my-function)))
   (unwind-protect (progn (fmakunbound 'my-function)
                          (fboundp 'my-function))
     (setf (symbol-function 'my-function) saved-definition)))
→ false
 (fboundp 'my-function) → true
 (defmacro my-macro (x) `',x) → MY-MACRO
 (fboundp 'my-macro) → true
 (fmakunbound 'my-function) → MY-FUNCTION
 (fboundp 'my-function) → false
 (flet ((my-function (x) x))
   (fboundp 'my-function)) → false

Side Effects:

None.

Affected By:

None.

Exceptional Situations:

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

See Also:

symbol-function, fmakunbound, fdefinition

Notes:

It is permissible to call symbol-function on any symbol that is fbound.

fboundp is sometimes used to “guard” an access to the function cell, as in:

(if (fboundp x) (symbol-function x))

Defining a setf expander F does not cause the setf function (setf F) to become defined. Moon wanted this removed because he thinks it is "redundant and pompous". -kmp 4-Dec-91 as such, if there is such a definition of a \term{setf expander} \param{F}, the \term{function} \f{(setf \param{F})} can be \term{fbound} if and only if, by design or coincidence, a function binding for \f{(setf \param{F})} has been independently established.