Often times I need to know about the lambda-list of a function for some kind of automatic construction business. Since this is implementation-dependant and SWANK isn't always handy, there's this.
(arg:arglist 'gethash) (arg:arglist #'gethash) (arg:arglist '(setf gethash)) (arg:arglist #'(lambda (foo) (declare (ignore foo))))
And that's all there is to it. If the lambda-list could not be determined,
:unknown is returned instead.