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From: dowding@ai.sri.com (John Dowding)
Newsgroups: comp.lang.prolog
Subject: Compiler smartness?
Message-ID: <DOWDING.90Nov16140150@palm.ai.sri.com>
Date: 16 Nov 90 22:01:50 GMT
Sender: news@unix.SRI.COM
Distribution: comp
Organization: SRI International, Menlo Park, CA
Lines: 29


I was poking around in some old code, and came across the following
clauses (names changed to protect the inocent):

foo(Term, Term):-
	(var(Term) ; atomic(Term)),
	!.
foo([Head|Tail], Result):-
	...


I was wondering if the following is more efficient:

foo(Term, Term):-
	var(Term),
	!.
foo(Term, Term):-
	atomic(Term),
	!.
foo([Head|Tail], Result):-
	...


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

Thanks,
John Dowding
dowding@ai.sri.com