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Date:Mon May 20 00:36:06 1999 
Subject:Re: Poplog sources 
From:Aaron Sloman See text for reply address 
Volume-ID:990520.01 

"Jonathan L Cunningham" <jlc@sofluc.demon.co.uk.spam> writes:

> Date: Tue, 11 May 1999 12:59:12 +0100
>
> >Poplog (including Pop-11) is shortly to become available free of
> >charge. I don't know exactly when -- see
> >    ftp://ftp.cs.bham.ac.uk/pub/dist/poplog/poplog.info.html
>
>
> That's good news.
>
> I had a quick look at this reference, which says
>  "Poplog (V15.53) including sources ... details still have to be worked out"
>
> Do you know if this will include all the sources?

My understanding is that all the system sources of all versions of
Poplog will be freely available (including the PC/windows version).

> Presumably you will
> need at least one working poplog already in order to recompile and
> link poplog,

Yes: most of the system is implemented in an extended dialect of
Pop-11 (supporting a number of C-like features for efficiency).

Anyone wanting to use those sources to build a new version will also
need quite a lot of knowledge about the system because of the rather
complex boostrapping process required to build Poplog.

I think that it will take quite a long time before there is a
sizable community of experts.

> so it is conceivable that "sources" refers only to all
> the libraries, but not, e.g., the source file(s) for the garbage
> collector.

It will all be there. Both garbage collectors actually (it has both
a stop-and-copy garbage collector, which is very fast, and a
slightly slower compacting/shuffling garbage collector for use when
there's a shortage of swap space or when paging is slow.

> There is also the issue of divergent poplogs, if all the sources
> are released and people start making incompatible changes. (I guess
> version control is a problem for bug fixes to libraries anyway.)

I hope a small band of enthusiasts can come forward to help decide
which fixes/changes should go into a "standard" distribution. Other
people may produce their own.

I expect that various importantly changed versions will start
becoming available after a year or two, e.g. a version which does
not have such a tight integration with the Ved/Xved editor, but
supports any programmable editor communicating via sockets
(including Ved and Emacs.)

There may also be some divergence between poplog/pop-11 for use in
teaching AI/Cognitive science and new versions aimed at engineering
applications.

Regarding the former I would like to propose that my pattern prefix
"!" which convers lists containing "?" or "??" so that the pattern
variables are no longer words but identifiers should become a
standard autoloadable extension (as it has been for a few years here
in Birmingham).

That means that pattern variables can be lexically scoped or work
with sections, greatly reducing the number of bugs associated with
uses of the pattern matcher. See
    ftp://ftp.cs.bham.ac.uk/pub/dist/poplog/lib/readpattern.p
    ftp://ftp.cs.bham.ac.uk/pub/dist/poplog/help/readpattern

> It will be interesting to see what, if anything, happens.

I think it's now simply a question of people at Sussex finding the
time. I'll be seeing people from ISL and Sussex in a couple of days
and hope to learn more.

Aaron
===
-- 
Aaron Sloman, ( http://www.cs.bham.ac.uk/~axs/ )
School of Computer Science, The University of Birmingham, B15 2TT, UK
EMAIL A.Sloman AT cs.bham.ac.uk   (NB: Anti Spam address)
PAPERS: ftp://ftp.cs.bham.ac.uk/pub/groups/cog_affect/0-INDEX.html