Path: utzoo!utgpu!watmath!clyde!ima!think!barmar
From: barmar@think.COM (Barry Margolin)
Newsgroups: comp.lang.lisp
Subject: Re: LET vs. &aux
Message-ID: <33649@think.UUCP>
Date: 19 Dec 88 20:56:43 GMT
References: <4400007@uicslsv> <5727@polya.Stanford.EDU>
Sender: news@think.UUCP
Reply-To: barmar@kulla.think.com.UUCP (Barry Margolin)
Organization: Thinking Machines Corporation, Cambridge MA, USA
Lines: 22

In article <5727@polya.Stanford.EDU> caron@polya.Stanford.EDU (Ilan G. Caron) writes:
>The question is: why does &AUX even exist?

&AUX was presumably invented because Lisp programmers often found that
the first thing they did in a function was to bind a bunch of local
variables.  Putting these variable bindings into the lambda-list saves
an indentation level.

I sometimes use &AUX when I am modifying a function.  If I need to
invent a new variable for communication between one section and
another, I will often put it into the &AUX list rather than wrapping a
random portion of the function in a new LET, and then use a SETQ.  I
realize that it isn't really good style, but if the function is
complex it is often the safest way to modify it, rather than trying to
reorganize it more cleanly.


Barry Margolin
Thinking Machines Corp.

barmar@think.com
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