Path: utzoo!utgpu!water!watmath!clyde!bellcore!faline!thumper!ulysses!andante!princeton!udel!rochester!cornell!uw-beaver!teknowledge-vaxc!sri-unix!quintus!ok
From: ok@quintus.UUCP
Newsgroups: comp.lang.prolog
Subject: Re: Atom-based module systems
Message-ID: <963@cresswell.quintus.UUCP>
Date: 13 May 88 01:53:44 GMT
References: <136@vor.esosun.UUCP> <841@cresswell.quintus.UUCP> <365@aiva.ed.ac.uk> <531@ecrcvax.UUCP>
Organization: Quintus Computer Systems, Mountain View, CA
Lines: 23
Posted: Thu May 12 21:53:44 1988

In article <531@ecrcvax.UUCP>, micha@ecrcvax.UUCP (Micha Meier) writes:
> In article <943@cresswell.quintus.UUCP> ok@quintus.UUCP (Richard A. O'Keefe) writes:
> 	I don't know what is the current_op/3 table and how does the read/1
> 	predicate access it, but in any case even in Prolog, there is
> 	more information one might want to associate with a functor:
> 	counters, recorded terms, arrays (except for recorded terms
> 	extended data types, but they *are* used). Apart from that,
> 	there are Prolog extensions that might want to associate even
> 	more information with a functor. In SEPIA, we have introduced
> 	property lists exactly because of this.
> 
> --Micha
The current_op/3 table is the built-in predicate current_op/3, what else?

The point is that information about atoms and functors is held in
predicates.  Property lists in Lisp are something of a disaster (you
cannot use properties freely, but have to check that the system isn't
using the name you have in mind; I have been burned by this) and hash
tables in Common Lisp provide a *much* better approach.  Using
predicates in Prolog is the analogue of using hash tables in Common Lisp.
Using predicates, you can associate arbitrary chunks of information
*without* complicating the implementation of atoms and functors, and you
have to support predicates anyway!