Path: utzoo!attcan!uunet!ncrlnk!ncrcae!hubcap!gatech!cwjcc!tut.cis.ohio-state.edu!unmvax!ncar!noao!asuvax!nud!sunburn!dover!hume
From: hume@dover.uucp (Chris Hume)
Newsgroups: comp.lang.lisp
Subject: Basic Lexical Variable Question
Keywords: Lexical Variables, Binding
Message-ID: <611@dover.uucp>
Date: 20 Dec 88 22:59:13 GMT
Organization: Motorola Sector CAD, Mesa, AZ {dover}
Lines: 42


An incredibly naive question - the answer to which,
I suspect, may be that the question would not arise
given adequate understanding of the role of Lexical
Variables:

In the form below, is there any way to achieve the
binding for "value" without giving it an initial value?

(do ((computed nil)
     (value nil))
    (computed (print value))
    (setq value 1)
    (setq computed t))

I know that Lexical Variables are not considered to
be "bound" in the same sense that Special Variables
are.  It may further be a distinct ADVANTAGE that
they will always "represent" some value, but is the
notion of an UNINITIALIZED Lexical Variable somehow
a contradiction in terms?

Coming at the question from another direction:
the value below is, of course, 1 (and not 2.)

(let ((variable 0))
  (set 'variable 1)
  (setq variable (1+ variable)))

In this case "(set (quote variable) foo)" and
"(setq variable foo)" are NOT equivalent!

Is it even POSSIBLE for Common Lisp to provide
the functionality of "set" to Lexical Variables?

Thanks in advance, for any clarification.
Chris
-- 
Christopher N. Hume		Net: ...!sun!sunburn!dover!hume
MOTOROLA, Inc.		 	M/D: DOV05
2222 South Dobson Road		Tel: (602) 994-6835
Mesa, AZ  85202			FAX: (602) 994-6895