🚀 go-pugleaf

In article <3647@goanna.cs.rmit.oz.au>, ok@goanna.cs.rmit.oz.au (Richard A. O'Keefe) writes:
> In article <126688@kean.ucs.mun.ca>, jgarland@kean.ucs.mun.ca writes:
>> In article <3581@goanna.cs.rmit.oz.au>, ok@goanna.cs.rmit.oz.au 
> [I wrote]
>> > 	run(done) :- !.
>> > 	run(Event) :- /* Event ~= done */
>> > 	    exec_event(Event, NextEvent),
>> > 	    run(NextEvent).
>> > 		
>> > If exec_event/2 is determinate, this is determinate.
>> > If exec_event/2 is not determinate, this is not determinate.
>> > 
> this two-clause
> approach is determiniate and tail recursive (provided only that exec_event/2
> is determinate) so that >>>it runs in bounded stack<<<.
> 

> [this] is _precisely_ what the comment about wanting exec_event/2 to be
> determinate was _about_.

I have no disagreement with this at all.  My point is that if the 
exec_event/2 clauses are ordered such that the last clause, and only 
the last clause, contains the recursive call on all iterations but the last, 
*it does not matter*  (to the PDC compiler anyway) that exec_event/2 is 
deterministic or nondeterministic.  No additional stack space is consumed on
each iteration, nor are any [additional] backtracking points generated.

Question:  Is this tantamount to saying exec_event/2 *is* deterministic for all 
practical purposes???  What am I missing?


John Garland

jgarland@mun                              Bitnet
jgarland@kean.ucs.mun.ca                  Internet