🚀 go-pugleaf

In article <587@gould.doc.ic.ac.uk>, cdsm@ivax.doc.ic.ac.uk (Chris Moss) writes:
> In article <GARY.89Jan24170950@milo.mcs.clarkson.edu> gary@milo.mcs.clarkson.edu (Gary Levin) writes:
> >Does anyone have access to source for IC-Prolog or any of its
> >descendants?  What machines will it run on?
> 
> The answer is probably NO. I asked Frank McCabe, the author, last
> year if he had the sources and he said he hadn't.

When I was at the University of Edinburgh we had IC-Prolog up for a while (I
think it was on the DEC-10).  I had a listing, but when I left Edinburgh I'm
afraid I threw it away.  It was a research program, not a production tool, &
was very slow indeed.  PARLOG incorporates some of the IC-Prolog ideas, but
not I think the ones gary@milo is interested in.  One idea which IC-Prolog
incorporated was to let you have several control-variants of a clause: you
could include several copies of a clause which differed only in the order of
the goals in the body, each to be used for a different instantiation pattern
(mode) of the head.  I have not seen this imitated since.  Perhaps NU-Prolog
may come closest?

Note that having a predicate
	times(A,  B, A_times_B)
is not all joy.  Successor and plus are ok, but times takes you out of the
decidable fragment of arithmetic.  Note that
	times(X, 0, 0)
has *infinitely* many solutions.  Such a thing in NU-Prolog would have to
wait until someone else comes up with a binding for X.  Even for
	times(X, Y, 720)
--720 being a rather small number-- the number of solutions is large.  In
fact, if we define times/3 to have the rationals as its domain rather than
the naturals, any query having more than one variable would have
infinitely many solutions.  This really isn't a property you want in your
primitive operations!

[This is being sent from a MicroVAX, courtesy of the University of Auckland.
 What an *atrocious* keyboard DEC have come up with!]