Path: utzoo!attcan!uunet!yale!krulwich-bruce
From: krulwich-bruce@CS.YALE.EDU (Bruce Krulwich)
Newsgroups: comp.lang.lisp
Subject: Re: What's the value of lexical scoping?
Message-ID: <31720@yale-celray.yale.UUCP>
Date: 17 Jun 88 17:12:02 GMT
References: <24508@ucbvax.BERKELEY.EDU> <515@dcl-csvax.comp.lancs.ac.uk> <199@esosun.UUCP> <525@dcl-csvax.comp.lancs.ac.uk>
Sender: root@yale.UUCP
Reply-To: krulwich-bruce@CS.YALE.EDU (Bruce Krulwich)
Organization: Yale University Computer Science Dept, New Haven CT  06520-2158
Lines: 32

In article <525@dcl-csvax.comp.lancs.ac.uk> simon@comp.lancs.ac.uk (Simon
Brooke) writes:
>If you wish to gain information from your environment, then clearly, the
>names of the symbols you use do matter. If you bind your locals either
>in an arg list or in a let statement, then they don't matter. If you
>*don't* do this, then you are using globals, which will get you into equal
>trouble no matter what binding scheme you use.

This is simply not true, especially when using programming techniques
encouraged in lexically scoped LISPs.  Suppose you pass around a function.
In a lexically scoped LISP such a function can reference variables from the
function that created it.  In a dynamically scoped LISP this variable
references can be blocked by other variables in the system.  This is
something you may not have done, having not worked with lexically scoped
LISPs, but it is incredibly powerful.  (See, for example, the book AI
PROGRAMMING, by Charniak et al.)

>>HAVE YOU EVER USED LISP????? 
>Yes. Why do you think I care about it so much?

There is a big difference between the capabilities available (and thus the
techniques used) in modern LISPs as opposed to older LISPs.  I really
suggest looking at AI PROGRAMMING or a similar book before claiming that
such capabilities are not needed.


Bruce Krulwich

Net-mail: krulwich@{yale.arpa, cs.yale.edu, yalecs.bitnet, yale.UUCP}

	Goal in life: to sit on a quiet beach solving math problems for a
		      quarter and soaking in the rays.