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From: rogers@eagle.SRC.Honeywell.COM (Brynn Rogers)
Newsgroups: comp.lang.lisp
Subject: Summing a list
Message-ID: <10794@srcsip.UUCP>
Date: 25 Oct 88 13:33:42 GMT
References: <1131@amelia.nas.nasa.gov> <5671@eagle.ukc.ac.uk>
Sender: news@src.honeywell.COM
Reply-To: rogers@eagle.UUCP (Brynn Rogers)
Organization: Honeywell Systems & Research Center, Camden, MN
Lines: 29


 I Have a silly question.   I need to take the sum of a list 
 of numbers.
 (SETQ NUMLIST '(1 2 3 6 7))
 This is quite simple, really, but what is the BEST way to do it?
 I like: 
 
 (EVAL (CONS '+ NUMLIST))

 But someone else says this would be faster::
  
 (LET ((SUM 0))
    (DOLIST (NUM NUMLIST)
       (SETQ SUM (+ SUM NUM))))  ;; or maybe (INCF SUM NUM)


of course, there is always:

(DEFUN SUM (NUMLIST)
   (COND ((NULL NUMLIST) 0)
         (T (+ (FIRST NUMLIST) (SUM (CDR NUMLIST))))))

    I think it's obvious that the last would be slow.
    Also it's Obvious that there are Many ways to do this.
What is the BEST (for speed and/or elegance) way to sum a list??

(I Run Gold Hills Common 3.0 on a Compaq 386/20 with a 387)

Thanks,    Brynn Rogers   rogers@src.honeywell.com