HDTenEightyP/NetNews huggingface dataset:
From: ridoux@irisa.fr (Olivier Ridoux)
Subject: Unification of rational terms
Organization: IRISA, Rennes (Fr)
Date: Wed, 23 Dec 92 10:04:38 GMT

Bart Demoen writes:
> Supporting rational tree unification (and conservation of sharing during
> some built-in predicates - which is a consequence of fully supporting cyclic
                                        ^^^^^^^^^^^
> terms) can actually speed up some programs quite a lot.

WEll, Well, well.  I like to be shightly more precise and show that
rational term unification and conservation of sharing are rather
independent.

The minimum that rational tree unification must do is to remember
every pair of equivalent terms in the current branch of the current
unification problem.  It will not buy you much conservation of
sharing.  The maximum it can do is to remember every pair of
equivalent terms in the current branch of the search-tree.  This will
buy you the maximum conservation of sharing.

In this context, "equivalent" means "made equivalent by unification".
Those terms that are equivalent without the help of unification may
well never be recognised as equivalent.

One might want to stick to the minimum for avoiding special trailing
and backtracking operations for handling the storing and unstoring of
equivalent pairs, and to benefit from the recursive control of
unification.  However, modern Prolog implementations already have
these special operations (for handling contraints, term rewriting or
whatever ...).  It would be rather mean of these implementations not
to give the maximum.

Note also, that remembering pairs of equivalent terms in the current
branch of the search-tree is also feasible and usefull for finite term
unification.  It improves memory representation and unification (if it
is smart enough to detect physically equal terms).

Moral: rational term unification and conservation of sharing are
rather independent issues.  Even if they use similar techniques.

Hoping it helps,

Olivier Ridoux

Newsgroups: comp.lang.prolog
From: mj@cs.brown.edu (Mark Johnson)
Subject: Re: Occurs check
Organization: Brown University Department of Computer Science
Date: Mon, 21 Dec 1992 15:31:47 GMT

>  In a more perspicuous description of Prolog-style Horn clause programming,
>I think it's a good idea to separate the constraint system from the
>resolution mechanism. Thus Prolog (in the simplified version here considered),
>whatever the constraint system used, delivers answers to a question A(x)
>of the form C(x,y), where C(x,y) is a conjunction of constraints, and
>it always holds that
>
>    (1)                     C(x,y) -> A(x)
>
>is a logical consequence of the program, read as a set of Horn clauses. Of
>course (1) does not imply that there is an x such that A(x); for this to
>follow, the constraint theory must be used.

This is a nice way of viewing things, but I don't know any Prolog that
gives you all of the constraints C.  Consider the following program:

	p(a) :- q(X,X).

	q(Y, f(Y)).

One the query p(X), Sicstus returns the following:

| ?- p(X).

X = a ? ;

no
| ?- q(X,X).

X = f(f(f(f(f(f(f(f(f(f(f(f(f(f ...
 
That is, sicstus only returns constraints related to variables appearing
the goal.  But the constraints that only have cyclic solutions may be
associated with other variables.

On a related issue, are there systems that permit user-specified
constraints, perhaps by means of some kind of escape system built
into the unifier?

Mark


Mark Johnson
Cognitive Science, Box 1978
Brown University
Newsgroups: comp.lang.prolog
From: jamie@cs.sfu.ca (Jamie Andrews)
Subject: Re: Occurs check (really constraints)
Organization: CSS, Simon Fraser University, Burnaby, B.C., Canada
Date: Wed, 23 Dec 1992 01:09:30 GMT

In article <1992Dec21.195646.3776@cs.brown.edu> mj@cs.brown.edu (Mark Johnson) writes:
|P.S.  I'm interested in this approach.  I know of work by 
|Hoefeld and Smolka ``Definite Relations over Constraint Languages'',
|and Chen and D.S. Warren ``C-Logic of Complex Objects'' and
|``Abductive Logic Programming'' that describe the decomposition
|into a relational and constraint components. Any other pointers
|to relevant literature?

     One other I know of is "Constraint Simplification Rules",
by Thom Fruehwirth (thom@ecrc.de), ECRC tech report 92-18.
He describes a framework of delay declarations and special
clause-like rules which are used by the system to store and
simplify constraints.  It looks like a very general system.

--Jamie.
  jamie@cs.sfu.ca
"The Tao's net encompasses the whole universe."  - tao te ching
From: cduguay@lcraft.ersys.edmonton.ab.ca (Claude Duguay)
Newsgroups: comp.lang.prolog
Subject: Re: Trilogy vendor in UK or Europe?
Date: Fri, 25 Dec 92 20:32:21 MST
Organization: LogiCraft Corp, Edmonton, AB, Canada

mfuerst@news.cecer.army.mil (Michael Fuerst) writes:

> cduguay@lcraft.ersys.edmonton.ab.ca (Claude Duguay) writes:
> 
> >fred@opal.cs.tu-berlin.de (Reinhard Arlt) writes:
> 
> >>Who markets Trilogy in the UK?  Or in Europe?  I rang the "Complete Logic
> >>Systems" USA number listed in the resource guide, but got no reply.
> >>I just want to play around with constraint solving, and can't afford CHIP.
> 
> >I can't tell you what their address is but Trilogy was developed by a
> >Canadian company based in Vancouver, BC. You migth be able to get the
> >number from directory assistance and information about distributors directly
> >through them.
> 
> >Claude Duguay              cduguay@lcraft.ersys.edmonton.ab.ca 
> 
> TRILOGY probably doesn't exist as a product.   The original product was 
> developed by a professor at University of British Columbia.  His product was 
> incomplete and buggy.   He sold the rights to another company which pur out
> a version called TRILOGY VS, but the partners could never make it commerciall
> complete, and they went broke.   One of the pricipals is now a stockbroker wh
> told me that he has several hundred copies of TRILOGY VS in his basement, and
> that he had lost $50K on the venture.  The professor of course did quite well
> I had spokent ot him also.  He issued flyers announcing a new vesion of TRILO
> the product.   All this is quite unfortunate, because its could have been qui
> Parkerford, Pennsylvania 19457, USA puts out a similar product called Expert 
> Thinker for $149.    It's written in Turbo Prolog and either assembler or C.
> Their phone is 215-495-6362
>  

Interesting! When Vertical solftware took over VS Trilogy, they contacted me
and, since I'd built a toolbox for Turbo/PDC Prolog, asked if I'd be willing
to do one for them. I said I'd be willing to consider it and they sent me a
demo but requested that I pay for the end-product. To which I decided a) I
did not want to do business with a company that wasn't willing to make a
reasonable effort and was so hard-up for money that they wanted to charge me
to develop a set of tools for their program, and b) I didn't think the market
was big enough, restricted as the Turbo/PDC Prolog market already was. It's
really too bad because I really liked the C-Prolog combination of Trilogy,
conceptually anyhow...

Claude Duguay              cduguay@lcraft.ersys.edmonton.ab.ca 
Newsgroups: comp.lang.prolog
From: brock@cs.tu-berlin.de (Oliver Brock)
Subject: qprolog & Mrm
Organization: Technical University of Berlin, Germany
Distribution: comp
Date: Mon, 28 Dec 1992 14:39:14 GMT


I am looking for a Motif Resource Manager library for Quintus prolog.
Can anybody help me ?

Oliver Brock (brock@cs.tu-berlin.de)
From: pereira@alice.att.com (Fernando Pereira)
Newsgroups: comp.lang.prolog
Subject: Re: Occurs check
Date: 21 Dec 92 19:38:23 GMT
Article-I.D.: alice.24461
Reply-To: pereira@alice.UUCP ()
Organization: AT&T, Bell Labs

In article <1h4g5tINN5l6@eagle.dfki.uni-sb.de> smolka@dfki.uni-sb.de (Gert Smolka) writes:
>I seriously doubt that rational tree unification pays any significant
>efficiency penalties in practise over Edinburgh-style unification
>without occurs check.  As has been mentioned by Torkel before,
>UNIFICATION IN SICSTUS IS RATIONAL TREE UNIFICATION, and Sicstus seems
>to be rather efficient.
I don't know what "rather efficient" means without actual numbers to
back it up. But *all* the rational unification algorithms I know
of need to make and trail more assignments, and chase more pointers,
than the original Prolog unification without the occurs check.
I would be happy it it were shown *over a well-chosen mix of programs*
that the overhead in question is negligible. But I've not seen such
a demonstration. 
>However, given the efficiency and
>the clean *logical* status of rational tree unification, I would expect
>that rational tree unification is taken as default and finite tree
>unification is accommodated as a built-in predicate
.he reason is that the efficiency issues mentioned above have not
been addressed to everyone's satisfaction.
>By the way, was it Edinburgh or Marseille which first dropped
>the occurs check?
Marseille. A very detailed and interesting account of the design history
of the first Prolog, written by Alain Colmerauer and Philipe Roussel,
will appear in the forthcoming proceedings of the History of Programming
Languages Conference (April 1993). Their choice was based on the
considerations that I have mentioned before. However, Alain eventually
changed his mind, as shown by the exclusive use of rational unification
in Prolog II. Nevertheless, the efficiency tradeoffs might still be
different for fast compiled Prologs than for interpreted systems
like the original Prolog and Prolog II: when the cost of clause
chasing goes down, the relative cost of term chasing goes up.

Fernando Pereira
2D-447, AT&T Bell Laboratories
600 Mountain Ave, PO Box 636
Murray Hill, NJ 07974-0636
pereira@research.att.com
From: mj@cs.brown.edu (Mark Johnson)
Subject: Cost of cyclic unification?
Organization: Brown University Department of Computer Science
Date: Wed, 23 Dec 1992 15:50:44 GMT

For two acyclic terms, can cyclic unification run in time proportional
to the size of the *smaller* term?

That is, if a program doesn't make use of cyclic terms then can it
run as efficiently on a Prolog that supports cyclic unification
as it would on a Prolog that doesn't support cyclic unification?

If true, it seems that cyclic unification would be preferable
to acyclic unification without the occur check.

Mark

P.S.: I constructed a small program to see if unifying two terms
of the form f(f(...f(f(_))...)) depended on the size of the larger
term.  I could detect no change in time required in Sicstus.


Mark Johnson
Cognitive Science, Box 1978
Brown University
From: chik@icot.or.jp (Takashi Chikayama)
Newsgroups: comp.lang.prolog
Subject: Re: ICOT 5th Generation Project Catalog
Date: 28 Dec 92 01:53:51 GMT
Reply-To: chikayama@icot.or.jp
Organization: Institute for New Generation Computer Technology, Tokyo, Japan.

In article <BzoFM8.96s@csulb.edu>
	werts@aardvark.cecs.csulb.edu (Michael Werts) writes:

 |How do I find out about the software released into
 |the public domain by the 5th Generation project?

Write to "ifs@icot.or.jp".  Or, you can just try anonymous ftp from
"icot.or.jp".  General information can be found in README (9686 bytes)
and INFO.tar.Z (19333 bytes).

Takashi Chikayama (ICOT)
Xref: sparky comp.lang.prolog:2289 comp.theory:2745
From: naiwei@cs.arizona.edu (Nai-Wei Lin)
Newsgroups: comp.lang.prolog,comp.theory
Subject: CASLOG is available
Keywords: Automatic Complexity Analysis, Logic Programs
Date: 21 Dec 92 22:01:21 GMT
Followup-To: poster
Organization: U of Arizona CS Dept, Tucson


	CASLOG - A Complexity Analysis System for Logic Programs

The CASLOG system is now available. 

CASLOG (Complexity Analysis System for LOGic) is an experimental 
semi-automatic complexity analysis system for logic programs. 
It can perform the worst-case analysis for complexity measures: 
argument size complexity, number of solutions complexity, and 
time complexity.

CASLOG extends the techniques developed for analyzing imperative and 
functional languages to deal with nondeterminism and generation of 
multiple solutions via backtracking in logic languages. The analyses
for different complexity measures are implemented in a unified framework
and share several common features. First, the predicates in a program
are processed in a order generated by a bottom-up topological sorting 
over the call graph of the program. Second, the complexity function for
a predicate is derived from the complexity function of its clauses by
using the information about the mutual exclusion relationships between
its clauses. Third, the complexity function for a clause is inferred
based on the data dependency relationships between its literals. Fourth,
the complexity functions for recursive clauses are in the form of
difference equations and are transformed into closed form functions using
difference equation solving techniques. This unified framework can 
simplify proofs of correctness and the implementation of the algorithms.

This unified framework is further enhanced by incorporating the ability of
using graph-theoretic methods to analyze the number of solutions complexity
for predicates that consist of constraints over finite domains. 
Given domain information, the system can handle predicates involving
linear arithmetic constraints and binary disequality constraints.

This release is an alpha release. It contains the CASLOG version 1.0,
a preliminary user manual, a paper on CASLOG, and a set of examples.
The system is available by anonymous ftp from

cs.arizona.edu

in the directory caslog.

Nai-Wei Lin					 
Department of Computer Science
The University of Arizona
Tucson, Arizona 85721
USA
naiwei@cs.arizona.edu
Newsgroups: comp.lang.prolog
From: torkel@sics.se (Torkel Franzen)
Subject: Re: Occurs check
Organization: Swedish Institute of Computer Science, Kista
	<TORKEL.92Dec21175440@bast.sics.se>
	<1992Dec21.195646.3776@cs.brown.edu>
Date: Mon, 21 Dec 1992 21:08:32 GMT

In article <1992Dec21.195646.3776@cs.brown.edu> mj@cs.brown.edu 
(Mark Johnson) writes:

   >P.S.  I'm interested in this approach.  I know of work by 
   >Hoefeld and Smolka ``Definite Relations over Constraint Languages'',
   >and Chen and D.S. Warren ``C-Logic of Complex Objects'' and
   >``Abductive Logic Programming'' that describe the decomposition
   >into a relational and constraint components. Any other pointers
   >to relevant literature?

  The theoretical treatment of constraint logic programming has been
solidifying lately, and there are several related formal frameworks.
I think a "standard treatment" may well soon emerge. My remarks have
been prompted by work here at SICS on AKL (the Andorra Kernel
Language), which has a reasonable concurrent constraint logic
programming subset. The theory of that subset is quite close in many
ways to the work of Hoefeld and Smolka, but there are some points of
difference in the formal treatment, partly having to do with concurrency.
A paper on this has been in the pipeline for a long time and may or may
not eventually emerge; those who are fanatically interested in this sort
of thing can get a copy directly from me.

Newsgroups: comp.lang.smalltalk
From: chuayap@rahul.net (Evan Chua-Yap)
Subject: Info requested re Finite State machines
Keywords: ST-80 recursive-finite-State-Machines
Organization: a2i network
Distribution: usa
Date: Tue, 29 Dec 1992 17:32:03 GMT


We are looking for information or code about recursive finite state
machine implementations for Parcplace ObjectWorks.  Please reply
by posting news or by email to:
      chuayap@rnd.brooks.af.mil
Thanks very much for the help!!
-- 
Evan Chua-Yap <chuayap@rahul.net>
Newsgroups: comp.lang.smalltalk
From: protocom@DMI.USherb.CA (protocom-Laurent turcotte)
Subject: Teaching kids/adults OOP concepts
Organization: Universite de Sherbrooke -- Dept. d'Informatique
Distribution: usa
Date: Sat, 2 Jan 1993 04:58:22 GMT


I'm looking for ANY info about TEACHING OOP to kids or adults...
 
        -It could be done using smalltalk and turtle graphics...    
                                                                    
        -It could be done using hyperCard like programs...
 
        -It could be done with a book od some kind...

        -Anything (the sky is the limit)
                                                        
I'm thinking of doing a University school project on this
                                 
P.S. ANY FEED BACK ON THIS IS DEEPLY APPRECIATED NO MATER HOW SMALL
-- 
Larry Turcotte                           Internet:protocom@dmi.usherb.ca
computer science student/consultant
consulting company:Protocom              Is there anybody out there.....
From: Expertek@nesbbx.rain.COM (**)
Newsgroups: comp.lang.smalltalk
Subject: Re: Advice for Smalltalk/V on Mac
Date: 2 Jan 93 19:00:46 GMT
Article-I.D.: nesbbx.Expertek.0kw4
Organization: NESBBX Bulletin Board System
X-NewsSoftware: BBX-UMB 0.27a beta (Nov 30 1992)


Mr. Rector,
 
I too have noticed ``some'' of Digitalk's math problems in working with
my Zoom database product.  Of course accurate pointer arithmetic is
essential for databases to work.  The only problem I know for sure is the
bitShift on v/286 has transient errors which move based on adding program
lines to the image.  What other actual inaccuracies have you found?  (I'm
not so concerned about inefficencies.)
 
Thanks very much.
 
Kirk W. Fraser
Expertek
From: js@montaigne.lif.icnet.uk (Jack Shirazi <js@biu.icnet.uk>)
Newsgroups: comp.lang.smalltalk
Subject: Re: anything isKindOf: nil ==> true (Objectwork
Date: 21 Dec 1992 09:23:18 -0000
Organization: Imperial Cancer Research Fund
Distribution: world
NNTP-Posting-Host: montaigne.lif.icnet.uk

In article <92121618993@zone4.ocunix.on.ca> anthony@zone4.ocunix.on.ca (Anthony Lander) writes:
>Actually, since Object is a subclass of nil (go and look if you don't believe
>me), everything that inherits from Object is-a nil.  
>Anthony Lander                            anthony@zone4.ocunix.on.ca 
>
That got me at first when I looked in the browser and saw
"nil subclass: Object", but in fact this just denotes the fact
that when the message #superclass is sent to Object, nil is returned.
This does not mean that Object is a subclass of nil

-- 
       Jack               js@bison.lif.icnet.uk
                         
If you only have a hammer, you tend to see every problem as a nail.
                -- Maslow
From: steinman@hslrswi.hasler.ascom.ch (Jan Steinman - Bytesmiths, 3946)
Newsgroups: comp.lang.smalltalk
Subject: Re: PPS stand-alone executable ?
Date: 31 Dec 92 07:10:58 GMT
Reply-To: steinman@hslrswi.hasler.ascom.ch
Organization: Ascom Hasler AG

In article 5878@ktibv.uucp, mjhe@ktibv.uucp (M.J.H. Eersel) writes:
>Can anyone tell me if it is possible to build a stand-alone executable
>of an application with Objectworks 4.1/Visualworks 1.0 of ParcPlace Systems ?

I've done it on a Mac. The VM only uses the resource fork, and the VI only
uses the data fork, so you can combine them into one file.

On all other machines, you're stuck with two files.

: : Jan Steinman, Bytesmiths			   steinman@hasler.ascom.ch : :
: : 2002 Parkside Court, West Linn, OR 97068-2767 USA	    +1 503 657 7703 : :
: : Beundenfeldstrasse 35, CH-3013, Bern, Switzerland	    +41 31 999 3946 : :
From: cshaver@informix.com (Craig Shaver)
Newsgroups: comp.lang.smalltalk
Subject: Re: Smalltalk/V for Sun (Sparc)
Date: 24 Dec 92 00:04:27 GMT
Organization: Informix Software, Inc.

In article <BzDFoJ.CB1@dale.cts.com> glippert@dale.cts.com (George Lippert) writes:
>Chuck Irvine (irvine@ntmtv.UUCP) wrote:
>> I vaguely seem to recall hearing something about Digitalk doing a port
>> of ST/V for the Sun Sparc. Does anyone know if there's any substance to
>> this? Any information is much appreciated. Thanks
>
>I talked with Digitalk about two days ago (I wanted them to port to the NeXT)
>and they told me that they where making their first foray into the world of
>Unix and that, based on user demand, they were going for the IBM RS/6000!  No
>definite plans about further platforms.
>
I think there may be some IBM $$$ involved that forced them to do the port.
Same reason they are throwing away resource on the OS/2 2.0 and Parts ports
rather than making an appropriate (for the market share IMHO ;') effort on
the mess dos windoz product.

-- 
Craig Shaver  (cshaver@informix.com for now) (415)390-0654 (415)926-6407
Productivity Group POB 60458 Sunnyvale, CA  94088
From: Expertek@nesbbx.rain.COM (**)
Subject: Re: anything isKindOf: nil ==> true (Objectwork
Newsgroups: comp.lang.smalltalk
Distribution: world
X-NewsSoftware: BBX-UMB 0.27a beta (Nov 30 1992)
Date: 26 Dec 92 11:07:14 PST
Organization: NESBBX Bulletin Board System


Some of these discussions seem silly, but:
 
There is only one instance of nil.  Every occurance of the statement nil
links one to the same instance.  I agree that since nil is a slotholder
for Object superclass, it cannot be said to inherit from nil conceptually
but it would be worth a try to see :-) if all objects respond to all nil
messages except where overridden.  If that's the case, nil would be a
case of multiple inheritance as UndefinedObject would inherit from itself.
 
Have fun following that!
From: sk3@doc.ic.ac.uk (S Karathanos)
Newsgroups: comp.lang.smalltalk
Subject: Advice for Smalltalk/V on Mac
Date: 21 Dec 1992 13:07:35 -0000
Organization: Department of Computing, Imperial College, University of London, UK.
Distribution: world
NNTP-Posting-Host: finch.doc.ic.ac.uk
Keywords: Smalltalk/V, Mac, Advice


Hello dear friends of Smalltalk,

my apologies for this request, I know that this is not a
marketplace, but I couldn't find the following information:

Smalltalk/V for the Mac:

* What are the requirements (68020? 68881? 4MB? 6MB? 20MB? System7?)
* How much does it cost? (Student rebate?)
* Where do I get it? (UK? Germany?)
* Somebody used it on the Mac? Can you recommend it?

I used an antique Smalltalk/V on the IBM-PC (oh dear) some time ago,
it ran under DOS with only 640K and was astoundingly fast and crashproof.
I simply loved it. Smalltalk80 from Parcplace doesn't run on my small
Mac Powerbook (needs the 68020 I think) and I guess it would be too
big and too slow anyway. Any ideas?

Thanks very for any advice

Stephan
From: ken@gunshy.ocunix.on.ca (Ken Walker)
Newsgroups: comp.lang.smalltalk
Distribution: world
Subject: RE: ST/V PM problems
Organization: OTI Ottawa
Date: Mon, 21 Dec 92 20:42:20 EST


In article <1992Dec15.082845.1578@uni2a.unige.ch>
dugerdil@uni2a.unige.ch () writes:

>
> Dear Netters,
...
> I run ST/V PM version 1.4 on OS/2 2.0. From time to time the Smalltalk
> system simply closes without any warning (but OS/2 does not crash). We

I have experienced the same thing and what usually clears it up is freeing
more disk space on your hard disk.  It is strange that neither OS/2 or
V PM issue any low memory or swap space storage dialogs.  Try that,
usually if I had less than 3 megs available this would happen.

---
NewsBrowser (v0.2)
Ken Walker, Software Engineer, Object Technology Int'l Inc.
EMAIL: ken@gunshy.ocunix.on.ca | ken@oti.on.ca
Phone: (613) 820-1200 Fax: (613) 820-1202
[self contents apply: Disclaimers standard] fork