5.3.4 fboundp [Function]

fboundp name => generalized-boolean

Pronunciation::

pronounced ,ef 'baund p\=e

Arguments and Values::

name—a function name.

generalized-boolean—a generalized boolean.

Description::

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

Examples::

      (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

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.