Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!samsung!uunet!munnari.oz.au!goanna!ok
From: ok@goanna.cs.rmit.oz.au (Richard A. O'Keefe)
Newsgroups: comp.lang.functional
Subject: Re: "Reverse Diff" Arrays
Message-ID: <6536@goanna.cs.rmit.oz.au>
Date: 27 Jun 91 07:31:46 GMT
References: <591sis-b@massey.ac.nz>
Organization: Comp Sci, RMIT, Melbourne, Australia
Lines: 19

In article <591sis-b@massey.ac.nz>, news@massey.ac.nz (USENET News System) writes:
> Would anyone else care to comment on why such a simple technique (at
> least in hindsight) appears to have received so little attention?

Possibly it has been regarded as too well known?  The technique was
applied to Prolog in a paper in the Uppsala conference (I've never had
the proceedings for that) in 83? 84? something like that.  There's a
small literature on multi-version data structures.

> Why
> bother with compile-time analysis to detect "single-threadedness" when
> a simple run-time organisation for arrays will suffice?

Because with reverse diffs you still have to keep the reverse diffs around
and maybe garbage collect later; with compile-time analysis you should be
able to generate exactly the same code you'd have had in an imperative
language.  (See Trilogy.)
-- 
I agree with Jim Giles about many of the deficiencies of present UNIX.