Re: [eclipse-clp-users] testing NOT existence

From: david <david_at_...151...>
Date: Thu, 15 Apr 2010 21:04:40 +0800
Kish Shen schrieb:
>> Hi Christian,
>> not/1 and \+/1 behave exactly the same -- I believe \+/1 was added
>> because not/1 does not do negation as some people understand it, so
>> \+/2 is considered by some to be a better name for the way Prolog (and
>> thus ECLiPSe) implements negation. Specifically, negation as failure
>> (with closed world assumption).
While we're on the topic, is there a way to test for the existence of a 
term while avoiding any use of rules that may have that term as the head?

For example, assume foo/1 is a dynamic predicate, and that there are 
rules such as:

   foo(X) :- goo(X).

Is there a way to test if there are any assertions of foo/1? One would 
want to avoid any "false positives" due to, say, goo/1 being satisfied.
Received on Thu Apr 15 2010 - 13:27:07 CEST

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