Newsgroups: comp.lang.apl
Path: watmath!watserv2.uwaterloo.ca!torn!cs.utexas.edu!convex!convex!metzger
From: metzger@convex.com (Robert Metzger)
Subject: Re: John Heckman and scans in APL
Sender: usenet@news.eng.convex.com (news access account)
Message-ID: <1993Feb13.215654.2476@news.eng.convex.com>
Date: Sat, 13 Feb 1993 21:56:54 GMT
References: <1993Feb8.234454.2638@yrloc.ipsa.reuter.COM> <1993Feb13.104524.3318@fid.morgan.com>
Nntp-Posting-Host: bach.convex.com
Organization: Engineering, CONVEX Computer Corp., Richardson, Tx., USA
Keywords: scan, Heckman, archaeology 
X-Disclaimer: This message was written by a user at CONVEX Computer
              Corp. The opinions expressed are those of the user and
              not necessarily those of CONVEX.
Lines: 24

In article <1993Feb13.104524.3318@fid.morgan.com> hui@fid.morgan.com (Roger Hui) writes:
>Bob Bernecky writes:
>
>> I am trying to track down John Heckman, who wrote the first scan 
>> functions in APL at least 20-some years ago. 
>
>In non-APL circles, this is known as the "parallel prefix algorithm". 
>It is applicable to any associative dyadic function, and was first 
>published by Richard Ladner in the SIAM Journal of Computing circa 1979.  

Presumably Bob is looking for an earlier reference than this, since I recall
**HE** footnoted Heckman as being responsible for these algorithms circa 1974
in an I.P. Sharp publication (the newsletter?).

There was a mathematically-oriented paper produced by someone at the IBM
Philadelphia Scientific Center in the early 70's that had a lot of nice uses
of scans.  Have you checked it?  (my copy is at home, otherwise I'd look it up).

/Bob
-- 
"There's nothing wrong with America that can't be fixed
 by impeaching Hillary's husband."
Robert Metzger			CONVEX Computer Corp.
Voice: 214-497-4437		Email: metzger@convex.com
