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From: bd@zyx.UUCP (Bjorn Danielsson)
Newsgroups: comp.lang.lisp
Subject: Re: A small brush fire ...
Message-ID: <217@zyx.UUCP>
Date: Wed, 26-Nov-86 19:25:53 EST
Article-I.D.: zyx.217
Posted: Wed Nov 26 19:25:53 1986
Date-Received: Thu, 27-Nov-86 02:01:09 EST
References: <8868@duke.duke.UUCP>
Reply-To: bd@zyx.UUCP (Bjorn Danielsson)
Organization: ZYX AB, Stockholm, Sweden
Lines: 32

In article <8868@duke.duke.UUCP> jds@duke.UUCP (Joseph D. Sloan) writes:
>
>	So how would you answer the following:  Since "good"
>programmers know better than using free (== global) variables,
>the argument between lexical and dynamic scoping is really a
>mute point.  The real issue this: Can you exhibit a piece of code
>that depends on the scoping rules that can't be coded AS WELL
>in a way that doesn't depend on the scoping rules?
>
>				duke!jds

Dynamic scoping is quite useful in code like:

(let ((*print-base* 2))
  (print (stuff)))

Or in general, when the dynamic binding of a global variable is used 
to pass a parameter to another function (in this case "print", or some
function called by print), but the variable is never accessed locally.

In most other cases where free variables occur, you should use closures:

(defun consall (l list)
  (mymapcar (function (lambda (x) (cons x list)))
	    l))

Because the closure is created when the dynamically visible variable
"list" is the same as the lexically visible one, the difference between
the two kinds of scoping disappear.

-- 
Bjorn Danielsson, ZYX, +46 8 653205, ...mcvax!enea!zyx!bd