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Further information about poplog and Pop-11 is available at http://www.cogs.susx.ac.uk/users/adrianh/poplog.html http://www.cogs.susx.ac.uk/users/adrianh/pop11.html ftp://ftp.cs.bham.ac.uk/pub/dist/poplog/poplog.info.html http://www.cvg.cs.reading.ac.uk/poplog
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(You're using Ved to read this, right? :-)
[ir] No it's not, sorry. If that's what you're looking for then try comp.protocols.pop or comp.protocols.internet or something (but I don't actually know if they exist). Here's the charter for comp.lang.pop:
The group serves for discussions on the programming language Pop11, and related environments, libraries, languages and the Plug User Group.
Relevant topics, in this group, would cover all aspects of Pop11 programming (from novice questions to expert efficiency issues) and the current BSI standards effort (Pop9x), and how it relates to other languages of this type (e.g. GLOW, Pepper).
Also relevant would be conversations about the Poplog programming environment and its libraries. Eg.
OOP in Pop11 Flavours, or objectclass etc. and how they relate to
other OOP languages (C++, CLOS etc.)
X windows hacking in Pop11
Mixed language programming (eg. between Lisp/Pop11/Prolog/ML/C etc.)
that is supported in Poplog but isn't relevant for discussion in
other, pure language, groups
Techniques for Artificial Intelligence programming (it is an AI
language after all :)
and so on.
[jl] Yes, there's a name clash because both had a thing called POP2. It doesn't matter. The protocol is on POP3, the language is at Pop11, the language system is called POPLOG.
If you want to know more about the protocol, please read
1225 Rose, M.T. Post Office Protocol: Version 3. 1991 May;
16 p. (Format: TXT=37340 bytes)
To get this document, send a one-line mail message to
<mail-server@nisc.sri.com> with no subject:
SEND rfc1225.txt
[as] I have an incomplete draft introduction to Pop-11 which is currently available via anonymous ftp.
ftp ftp.cs.bham.ac.uk <login as "anonymous" with password your email address> cd pub/dist/papers get primer.Z quit
then
uncompress primer
[sfk] From the computer scientist's viewpoint, the most important qualities of Pop are :-
[sfk] I only know of one implementation for the PC and that's one called GLOW. I've only seen this system reviewed once in (wait for it ...) the UK section of Byte magazine & no one I know has tried it out. Alas, I've lost the relevant article. So, please please will someone post the contact details for the GLOW implementation?
Incidentally, GLOW is a fairly major deviant from the "mainstream" of Pop languages.
[as] The Brighton based company Cognitive Applications Ltd produced an implementation of Pop-11 called Alphapop, which was, I think, very favourably reviewed in Byte around May 1986 by Dick Pountain.
I think the price has dropped substantially since those days, especially for academics, though development froze some years ago, and it is now only a small though very usable subset of Poplog Pop-11. For more information contact:
Cognitive Applications Ltd 4 Sillwood Terrace Brighton BN1 2LR +44 (0) 273 821600
[rl] AlphaPop (Pop11 for the Macintosh) - the prices:
The standard AlphaPop package includes: Software Language Guide book Reference Manual book
A single user license costs L400; academic price L300. Additional licenses are quite cheap, and the 25% academic discount applies across these also.
There is a 'student edition'. It includes: Software Electronic version of reference manual
(it is intended for people who are being taught Pop11, and therefore don't need the full tutorial documentation)
This edition costs L120, and is available to bona-fide students.
(All prices exclude VAT).
AlphaPop - the version (also, AlphaPop - the Caveat):
The current version of AlphaPop is 1.2.3. We have never charged anyone for an upgrade; and have always tried to contact all known customers when there was an upgrade; if anyone still has an older version, please send me the disk (Ben Rubinstein at Cognitive Applications, address below) and we will upgrade you.
This version of AlphaPop has basic graphics facilities. It does not support colour, QuickTime etc. It runs under System 7, but does not run with 32-bit addressing switched on. It runs under every operating system from 3.4 to 7.1, and on every known Macintosh (current and discontinued), most of which have been introduced since it shipped. It runs happily on a 512K Mac; and can take advantage of more memory, up to 8MB.
Now the caveat: anyone buying AlphaPop should be aware that we have no plans to upgrade it further. As noted above, there seems every reason to believe it will continue to be compatible for some time to come; but we can't guarantee it, nor should you expect upgrades to take advantage of new features such as QuickTime. We do not actively market AlphaPop, but are happy to sell it to anyone who enquires, provided this is understood.
AlphaPop - the contact address:
(In the US + Canada, please contact:
Computable Functions Inc.,
35 South Orchard Drive
Amherst MA 01002
USA
Tel: (413) 253-7637
)
Outside North America:
Cognitive Applications Ltd
4 Sillwood Terrace
Brighton
BN1 2LR
Tel: 0273-821600 Fax: 0273-722767 EMail: UK0025@applelink.apple.com
[kers] So far as I know, there are no FTP'able versions of Pop at all. Pop also tends not to run on MS-DOS machines, historically (I think) because of their pig-poor addressing and underpowered CPUs; this has changed recently. (Poplog does run on Sequent Symmetrys, which are high-end *86's. I think.)
Some person somwhere was rumoured to be doing a Pop look-fairly-like called Saffron, or Karl, or Salt. Something like that. But I don't think they've done anything with it recently. Lazy frogs.
[sk] So, Chris, when is Pepper going public? (Karl?? Oh, Karl Popper.)
[es] The article on GLOW can be found in the UK May 1992 issue of Byte magazine, page 84UK-8.
For those who haven't got access to this issue, I will give a very brief summary, including quotes from the article:
"Glow Comes Out of the Dark" (Dick Pountain)
Inspired by POP-11, Glow is a powerful list-processing language for MS-DOS.
Glow, like its ancestor POP-11, is an interactive list-processing language with a syntax that resembles Pascal or structured BASIC. It supports loops as well as recursion, lists as well as strings, and objects with multiple inheritance.
A major difference between it an POP-11 is that Glow employs strictly lexical, rather than dynamic, scoping. This means that the visibility of any object is governed by the program text (as in Pascal), rather than the run-time environment.
MS-DOS Glow calls your own external text editor from inside Glow and compiles directly from the editor, so long as it is not too large.
One difference is in definition of procedures: instead of POP's
define ... enddefine
Glow uses
def ... edef
Glow performs I/O via two streams called "source" and "sink" which you redirect as necessary to real I/O devices, called IODEVS (e.g. console,keyboard,stderr ...).
The first-release version of Glow that I have is stable, but has some rough edges ...
Glow is the BASIC of AI languages.
Glow for Macintosh or MS-DOS with manual and user's guide, 69.95 pounds, from
Andrew Arblaster NightOwl software Bollostraat 6 B-3140 Keerbergen Belgium 32-015-234871 fax:32-015-234871
[sfk]
The key difference between Lisp and Pop's semantics (putting the important issue of syntax aside for one moment) is the open stack.
.... Having the open stack at the heart of all programming idioms gives the language family its distinctive character.
One idiom will illustrate my point nicely. The task is (say) to add all the numbers in a list. One of the built-in routines is called "applist" which takes a list and a procedure as arguments. It then applies the procedure to each element of the list in turn. We can add all the numbers in the list as follows:
applist( 0, LIST, nonop + ) ;;; nonop disables infix-ness of +
Oh? Did I say applist takes 2 arguments? Well, I did but don't forget that Pop uses an open stack, so there's no notion of argument checking. All the arguments go on the stack and come off again. This example works because the iteration starts with 0 on the stack, then element 1 gets pushed, then the top two items get added and replaced by the single result, and so on and so on. At the end of the iteration, all that remains on top of the stack is the answer.
Of course, the equivalent functional programming idiom (e.g. in Lisp) would be to define a slightly different higher-order operator to "applist" which might be called "fold".
define fold( sofar, list, op );
if null( list ) then
sofar
else
fold( op( sofar, hd( list ) ), tl( list ), op )
endif
enddefine;
That's always true. You can always do it in Lisp (or whatever) but you just do it differently. Here's another nice use of the open stack. Suppose we want to flatten a tree (represented as a list of lists) into (say) a list. What's the idiomatic way of writing that? The answer is to use the stack as a temporary collection zone.
define flatten_to_stack( tree );
if islist( tree ) then
applist( tree, flatten_to_stack )
else
tree
endif
enddefine;
define flatten( tree );
[% flatten_to_stack( tree ) %]
enddefine;
The virtue of writing flatten this way is that, for example, it might turn out that we didn't want a list but we wanted a vector (1D array). Well that was easy ...
define flatten( tree );
{% flatten_to_stack( tree ) %}
enddefine;
Changed my mind. I wanted to convert the vector into a string. Fine ...
define flatten( tree );
consstring(#| flatten_to_stack( tree ) |#)
enddefine;
Note the use of count brackets "#|" and "|#" in the above example. These simply count the difference in the length of stack before and after the expression between them. This makes sense when you know that consstring expects a count of the number of characters on the stack as its "topmost" argument.
This is probably far too long a post already but I could go on about the open stack for another couple of hours. It is the most wonderful thing about Pop and defines the language family. It is never the case that it makes you able to do things that can't be done in Lisp-like languages but it does make you want to say them rather differently!
[as] The Poplog Virtual Machine extends the simple Forth-like facilities of Pop-11 (push something onto the stack, pop the top of the stack into ..., call procedure X, return from current procedure, go to, branch if, etc. etc.) with quite a lot of sophisticated constructs including mechanisms for handling abnormal exits, interrogating the control chain, trapping procedure exit and entry (and running user-specified set-up and re-set procedures), handling both dynamic and lexical scoping, handling a stack of prolog continuations, runtime creation of new procedures, etc. The PVM makes it possible to implement incremental compilers for a variety of high level languages, not all with efficiency comparable to stand-alone implementations, but still quite tolerably fast, and much faster than if they were interpreted. (E.g. you can build a prolog interpreter in any Lisp system, but not an incremental prolog compiler.) For more on the Poplog VM see
Robert Smith, Aaron Sloman, John Gibson `POPLOG's two-level virtual machine support for interactive languages' in Research Directions in Cognitive Science Volume 5: Artificial Intelligence, eds D. Sleeman and N. Bernsen, Lawrence Earlbaum Associates, 1992 (Also Cognitive Science Research Paper 153, School of Cognitive and computing sciences University of Sussex, Jan 1990).
[ir] See HELP * POPREFS for more papers on Poplog
as - Aaron Sloman, Birmingham University
ir - Ian Rogers, Sussex University
jl - Jonathan Laventhol, D. E. Shaw & Co.
kers - Chris Dollin, HP Labs
rl - Rudi Lutz, Sussex University
sfk - Steve Knight, HP Labs
Now known as Steve Leach, at:
steve@bel.bel-epa.com
steve@watchfield.com
--- C.all/help/popfaq --- Copyright University of Sussex 1992. All rights reserved. ----------