Path: utzoo!mnetor!uunet!husc6!bloom-beacon!think!rlk
From: rlk@think.COM (Robert Krawitz)
Newsgroups: comp.emacs
Subject: Re: functionp
Message-ID: <15328@think.UUCP>
Date: 22 Jan 88 16:42:56 GMT
Sender: usenet@think.UUCP
Reply-To: rlk@THINK.COM
Organization: Thinking Machines Corporation, Cambridge, MA
Lines: 36

In article <8098@reed.UUCP> trost@reed.UUCP (Bill Trost) writes:
]In article <39315@ti-csl.CSNET>, ekberg@home (Tom Ekberg) writes:
]> ... How does the following definition appear to your critical eyes?
]> 
]> (defun functionp (object)
]>   "Returns t if OBJECT is a function."
]>   (cond ((subrp object) t)
]> 	((commandp object) t)
]> 	((listp object) (eq (car object) 'lambda)))
]	;modified to be cleaner lisp and to avoid line-counter problems
]
]Anyhow, what ya'll are most definitely looking is fboundp, which
]returns t if the argument has a function definition.  If you want to
]get at that definition, use symbol-function.  Be warned that macros

(keyboard macros, that is; not lisp macros, which are a list whose car
is 'macro)

]are strings attatched to the function definition, so you may want to
]check for that as well.

Fboundp checks that a SYMBOL has a function definition.  Bill has
something else in mind, namely checking that an OBJECT is a function.

Actually, a better way to write this is

(defun functionp (object)
  (or (subrp object)
      (commandp object)
      (and (listp object)
           (or (eq (car object) 'lambda)
               (eq (car object) 'macro)))))

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