Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!apple!voder!pyramid!leadsv!laic!vogon!ik
From: ik@vogon.laic.uucp (Ik Su Yoo)
Newsgroups: comp.lang.lisp
Subject: CL and lexical closures
Message-ID: <638@laic.UUCP>
Date: 26 Jul 89 16:22:02 GMT
Sender: news@laic.UUCP
Reply-To: ik@.UUCP ()
Distribution: usa
Organization: Lockheed AI Center, Menlo Park, CA
Lines: 25

It seems to me like whenever one uses #'(lambda ...), there is an
overhead because the form must remember its lexical environment.
Although I find these kinds of forms very useful, I still have
questions about their cost:

  1. How much cost is there for using lexical closures?

  2. Is lexical closure always created when using #'(lambda ...), or
     only when there is a free variable access within the form? If the
     former, does it save all bindings?

  3. [related to 2] Which of the following is more efficient?

       (defun store-fn (slot-name)
	 (setf (get slot-name 'lookup-fn)
	       #'(lambda (object)
		   (foo object slot-name))))

       (defun store-fn (slot-name)
	 (setf (get slot-name 'lookup-fn)
	       (eval `(compile nil
			       #'(lambda (object)
				   (foo object ',slot-name))))))

Thanks in advance for any insights.