Path: utzoo!utgpu!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!cwjcc!hal!nic.MR.NET!tank!uxc!uxc.cso.uiuc.edu!m.cs.uiuc.edu!uicslsv!bharat
From: bharat@uicslsv.cs.uiuc.edu
Newsgroups: comp.lang.lisp
Subject: LET vs. &aux
Message-ID: <4400007@uicslsv>
Date: 18 Dec 88 04:29:00 GMT
Lines: 23
Nf-ID: #N:uicslsv:4400007:000:1038
Nf-From: uicslsv.cs.uiuc.edu!bharat    Dec 17 22:29:00 1988


I am concerned with the relative efficiencies of using &aux and let
for using local variables (I usually use whichever seems to be more
aesthetically appropriate), but here are my opinions.

There should be little or no difference; however counterintuitively
the let block seems to be better in the case where the local is
accessed very often.

The &aux var. is (probably) affixed to the (end of) the binding list.
References to it within another lexical construct (say I am using both
a let and &aux) would probably have to assoc through the bindings,
while the let variables would be defined in the lexical block. So I
conclude that if you are going to use a let at the top level anyway,
it is probably more efficient to put all your local vars in the let,
rather than &auxing them.

Who am I kidding anyway - the short binding lists (with max 10-12
variables - local and otherwise) probably cause no appreciable
difference. Any comments?

Also what if I did &aux, followed by a setq (not within the variable
defn.) - which is better?