🚀 go-pugleaf

THANKS!
My humble question on how logic programming and object oriented 
programming styles could be combined turned out to be stated
vaguely enough to be answered in many ways. Certainly I have my own opinion, 
but there are always others who know other things than you do, and therefore
I thank you for being so kind to share your knowledge. 

STANDPOINT.
At this stage I am more interested in how parts of a system prototype
can be modelled on the language in question. That is not to say that I 
do not care about any theoretical discussions, about whether OOP and LP
mix at all and it what ways. 

PRAGMATICS.
It seems that one can get far by employing the same strategy of
a message-passing style for Prolog as Abelson and Sussman did in the
book "Structure and Interpretation of Computer Programs". Jonas Nygren
(below) showed how one can add syntactic sugar to Prolog and implement
inheritance. Mark Plotnick (below) mentions a company which has taken this
farther an sells a *product* built on top of Quintus. One step farther
and your over the edge into another language, which does not make things
better, but in my opinion, merely changes the view or performance.

THEORY?
Ulrich N. (below) reminded me of one aspect of the OO paradigm. 
Namely, that objects have states. Now, neither mathematical logic or 
lambda calculus on which we try to base pure logical and functional languages
 provide for something called states. It seems to me that something is 
missing here, and that concurrency as in GHC and the like has little to do 
with it. 

LETTERS.
Last but not least I have enclosed a list of references out of personal
letters:

Once again, thank you for your effort.
--Theo


-----------------------------------------------------------------------
Theo Kanter		ELLEMTEL Telecommunication Systems Laboratories
			Box 1505, S-125 25 [lvsj| (AElvsjoe), Sweden

			Office:	+46 8 727 35 93
			Fax   :	+46 8 647 82 76
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			Mail  :	Theo.Kanter@eua.ericsson.se




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From: norvell@csri.toronto.edu
Organization: CSRI, University of Toronto
-----------------------------------------

 >Take a look at Ait-Kacii's language  called Login.  It is described
 >in a MCC technical report and is about prolog extended with Inhertance.
 >In a similar vein, but more complex is David Maier's O-logic.

From: novick@ogicse.ogc.edu (David G. Novick)
Organization: Oregon Graduate Institute (formerly OGC), Beaverton, OR
---------------------------------------------------------------------

 >  P. Albert (1985).  Prolog et les objets.  Proceedings of the
 >  Fifth International Workshop on Expert Systems and their Application,
 >  Avignon, pp. 331-350.

 >  J. Conery (1988).  HOOPS manual.  Technical report, University of
 >  Oregon.


From: mark@infolog.se (Mark Plotnick)
Organization: Infologics AB, Box 91, 191 22 Sollentuna, Sweden.
---------------------------------------------------------------

Mark wrote that he knew about 2 commercial alternatives:

 > Prolog++ from LPA
 > LAP built on top of Quintus by a french company ELSA


From: yoshida@icot.or.jp (Yoshida Kaoru)
----------------------------------------

Commented Nils Hagner's respons to my article in the newsgroup, being 
the designer of A'UM.


From: Inst.f.Prakt.Info 1802 <brock@tuvie> (Ulbricht Neumerkel)
Organization: Technical University of Vienna, EDP-Center
--------------------------------------------------------

Wrote an interesting and lengthy letter. It's essence could be said to be
that OOP does not mix well with declarative programming. 
I am probably doing him injustice, whatever I write..
			 

From: jonas@falcon.ericsson.se (Jonas Nygren)
Organization: Ericsson Telecom, Stockholm, Sweden
-------------------------------------------------

Sent me a:

  > Sample POOPS class library: list{stack,queue,tree{binarytree{x}}}
  > In the spirit of same libraries described in 
  > Object-Oriented Software Constuction, B Meyer, Prentice-Hall 

Which essentially is syntactic sugar on top of Prolog, Jonas wrote.


From: ingvar@sics.se (Ingvar Olsson)
Organization: Swedish Institute for Computer Science, Kista, Stockholm
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Wrote that his approach in his current project was a pragmatic one,
and that he implemented a prototype using a message passing style
of programming. Sounds like it resembles my own strategy. I will
continue the discussions with Ingvar.