Path: utzoo!yunexus!geac!syntron!jtsv16!uunet!seismo!sundc!pitstop!sun!amdcad!ames!mailrus!tut.cis.ohio-state.edu!bloom-beacon!think!barmar
From: barmar@think.COM (Barry Margolin)
Newsgroups: comp.lang.lisp
Subject: Re: Summing a list
Message-ID: <29856@think.UUCP>
Date: 28 Oct 88 19:44:06 GMT
Article-I.D.: think.29856
References: <10794@srcsip.UUCP> <10813@srcsip.UUCP> <249@pitstop.UUCP> <3780@cs.utexas.edu>
Sender: news@think.UUCP
Reply-To: barmar@kulla.think.com.UUCP (Barry Margolin)
Organization: Thinking Machines Corporation, Cambridge MA, USA
Lines: 19

In article <3780@cs.utexas.edu> farquhar@cs.utexas.edu (Adam Farquhar) writes:
>For example, one would like to be able to say
>	(reduce #'+ (list box1 box2 box3 box4) :key #'box-weight)
>Does anyone know why :key was left out?  Is there an elegant way to do
>this in CL?

I don't know why :KEY was left out.  In my opinion, the best way to do
this currently is

	(flet ((+-weight (x y)
		 (+ (box-weight x) (box-weight y))))
	  (reduce #'+-weight ...))


Barry Margolin
Thinking Machines Corp.

barmar@think.com
{uunet,harvard}!think!barmar