🚀 go-pugleaf

In article <DOWDING.90Nov16140150@palm.ai.sri.com>, dowding@ai.sri.com (John Dowding) writes:
> I was wondering if the following is more efficient:
> 
> foo(Term, Term):-
> 	var(Term),
> 	!.
> foo(Term, Term):-
> 	atomic(Term),
> 	!.
> foo([Head|Tail], Result):-
> 	...

There is only one way to tell:  MEASURE IT AND SEE.

I am profoundly suspicious of a piece of code which tests for var, atomic,
and then list.  I suspect that there are far grosser efficiency issues to
worry about.  If it calls (=..)/2 you should eliminate that _first_.

> Are Prolog compilers (particularly, Quintus version 2.4) smart enough 
> index correctly on the 1st argument in either or both of these cases?

*CORRECTLY* yes, in that the code will work.  Was QP2.4 first-argument
indexing aware of type tests?  No.  Should you worry about that?  It
all depends on what the rest of your code is like:  if you have calls
to univ (=..) in there, you have more important things to worry about.

-- 
I am not now and never have been a member of Mensa.		-- Ariadne.