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Date:Mon Mar 2 19:31:30 1994 
Subject:Re: Author of Pop? 
From:"A.Sloman" 
Volume-ID:940302.04 

Ian (ianr@uk.ac.susx.cogs) wrote
> MICHAEL J PEPIN (mpepin@titan.ucs.umass.edu) wrote:
> > I was wondering if anybody could tell me the name of the author of the
> > Pop programming language?   Thanks.

> The 'POP' of Pop11, Poplog et cetera, is a Robin Popplestone, who, last
> I knew, was working in a university in Boston.

	University of Massachusetts, Amherst. Some way out of Boston!

"POP" stood for "procedure oriented programming" I think, and was also
a double joke, because of Robin's name and the importance of the stack
in the POP languages.

> There was no Pop3 to Pop10, to the best of my knowledge.

Pop10, which was used in several places between about 1974(???) and
about 1978( and beyond ???) was implemented by Julian Davies at
Edinburgh, to run on the PDP-10 computer. It was done independently of
the POP2 that was ported to the PDP-10, and had a lot of new features,
including better interrupt handling, a much better integrated editor
(designed by Bob Boyer and J Moore), used lower case by default, etc.
Some of the features were later taken over by other Pop implementations,
e.g. WPOP, Pop-11.

Some of the early versions of Pop2 had a version of setpop which merely
unwound the control stack without re-setting local variables (all of
which were dynamic in those days). That meant that after an error one
often could not get programs into any usable state and had to abort and
restart. I think Julian's Pop10 was the first implementation which fixed
this problem.

Ian attributed the next bit to me, but must have had an editing slip, as
I never wrote it, since I knew about Pop10 and used it for several
years, and I did not implement anything for the PDP10. Sounds as if it
may have been written by Ray Dunn? Ian, where did this comment come
from?
> [as] {NOT as!}
> I have no recollection of Pop10, but POP-2 (please notice the capitalisation
> and the hyphen) for the PDP10 (later known as the DECsystem 10) was
> implemented by myself and Malcolm Atkinson (now of Cambridge) in 1970 or
> 1971.


> Didn't Julian [Davies] implement an early version of POP-2 based
> Prologue?

Is this supposed to refer to Prolog?

See my report on Julian Davies above. The above comment is probably a
reference to this: Julian implemented a system called POPLER. It was
written in Pop2 (then later Pop10) and provided the most complete
implementation of the language PLANNER designed by Carl Hewitt at MIT
and reported in his PhD thesis around 1971.

At MIT there was a lisp-based subset called Microplanner (implemented by
some subset of McDermott, Winograd, and Sussman?) which was used by Terry
Winograd for his (then) world-shattering natural language processing
program Shrdlu.

POPLER was a larger subset of PLANNER, and Julian used it for his own
work on natural language. Only a few other people ever used Popler
because (by the standards of those days) it was very big, very resource
hungry and very slow. Also around that time, Sussman and McDermott
published their critique of PLANNER (which made heavy use of
backtracking, like Prolog). So people started switching away from
PLANNER (and therefore POPLER) to CONNIVER, which offered more flexible
and user-controllable processes. (Steve Hardy, at Essex University,
implemented a version of CONNIVER in Pop2 which he called POPCORN, which
he and several other people used for a while, including Sylvia Weir
at Edinburgh, who later moved to MIT to work on LOGO).

Julian subsequently went to Canada. His Pop10 system was used for a
while at the University of Western Ontario (e.g. by Zenon Pylyshyn and
others). Julian died of cancer in the mid 1980s alas.


> When you consider the research output of the DMIP in the late sixties and
> early seventies, it is difficult to believe that all the work was done on a
> machine with 64K 24-bit words, 2 microsecond add time, through model 33
> 10cps teletypes.

I used it in Edinburgh in 1972-3 during which time there was an amazing
increase in memory to 128K words... We had much rejoicing. However the
teletypes continued to work at 110 baud, with much noise, and much paper
consumed.

This bit looks as if it came from me!
> At Sussex, Frank O'Gorman later implemented a Pop2 in a mixture of
> Algol-68 and Pop2 for the ICL 1906A in the late 1970s. It was used
> for a while on a vision research project led by Max Clowes, using an
> ICL machine at the Rutherford Lab to which they had a remote
> connection.


> [ir]
> Hmmm, we seem to have gone from 1963 to 1672 but that's when the
> conversation stopped. I think Aaron could comment best on what happened
> after that at Sussex.

It is fully documented in
	Aaron Sloman,
	`The Evolution of Poplog and Pop-11 at Sussex University' in
	POP-11 Comes of Age: The Advancement of an AI Programming Language
	ed J. A.D.W. Anderson,
	Ellis Horwood, pp 30-54, 1989.

Cheers.
Aaron