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From: ok@goanna.cs.rmit.oz.au (Richard A. O'Keefe)
Newsgroups: comp.lang.prolog
Subject: Re: Garbage collecting names in Prolog
Message-ID: <5341@goanna.cs.rmit.oz.au>
Date: 23 Apr 91 01:49:35 GMT
References: <1991Apr5.143158.7857@swift.cs.tcd.ie> <5218@goanna.cs.rmit.oz.au> <1991Apr17.105714.7876@swift.cs.tcd.ie>
Organization: Comp Sci, RMIT, Melbourne, Australia
Lines: 30

In article <1991Apr17.105714.7876@swift.cs.tcd.ie>, brady@swift.cs.tcd.ie writes:
> In article <1991Apr16.124755.868@sics.se>, roland@sics.se (Roland Karlsson) writes:
> > The current_atom/1 and current_functor/2 assumes that you somewhere
> > have stored a set of atoms or functors.  What set????  In practice
> > those two predicates are meaningless and should not be implemented.

> This and previous messages are interesting. Does _anyone_ use
> current_atom or current_functor for anything?

The DEC-10 Prolog library includes a kit of things related to
Lisp's "apropos".  Amongst other things, there was no current_key/2
in DEC-10 Prolog, so

	current_key(Symbol, Skeleton) :-
		current_functor(Symbol, Skeleton),
		has_at_least_one_record(Skeleton).

	has_at_least_one_record(Skeleton) :-
		recorded(Skeleton, _Term, _Ref),
		!.

Basically, current_{atom,functor,predicate} were useful for building
program environment tools with.  As long as they include the relevant
things, which usually means "things in the data base", that's enough.
current_functor/2 is dispensible (if you have current_key/2), but
current_atom/1 has no substitute that I am aware of.

-- 
Bad things happen periodically, and they're going to happen to somebody.
Why not you?					-- John Allen Paulos.