Re: [rules-users] forall is satisfied when there is nothing?

forall is implemented as two notes, see the Clips documentation here. In reality it is just a bit of sugar for those two notes. You might be able to achieve what you want, with your own combination of nots. http://www.csie.ntu.edu.tw/~sylee/courses/clips/bpg/node5.4.7.html Mark On 8 Jan 2014, at 11:32, Sonata <plz.write.to(a)gmail.com&gt; wrote: > laune wrote >> On 08/01/2014, Davide Sottara &lt; > >> dsotty@ > >> &gt; wrote: >>> Indeed it is true by convention, see also >>> http://en.wikipedia.org/wiki/Universal_quantification >>> >>> The only other alternative is to deprecate quantifiers altogether ;) >>> >> >> Ah, *by convention*, yes. One should exercise some care with "vacuous >> truths", however. Uttering statements such as "All the little green >> men in my room are from Mars" may not brand you as a liar, but you >> could be called "batty". ;-) >> >> -W >> >>> Davide >>> > > Guys, I am not sure whats the arguing point here. But from a programmer's > and a Drools engine user's perspective, I would find forall(void) to return > false more convenient. > > Say for example: > forall(Cloth(dried)) then collect() > Programmingwise, I dont want to execute collect() when the Cloth() > collection is empty and do extra null checkings. > Performancewise, I also dont want to call collect() when there is actually > nothing to perform. > In terms of semantics, I purposely want to check for isDried is true, it is > easy to realize from the LHS that I only want to collect clothes when all of > them are dried, rather than I want to collect also empty air. > > On the contrary, if I really want to do the RHS even though the LHS has > nothing, I would have written: > not( exists( Customer() ) ) then takeanap() > and I will not write > forall( Customer(status == "gone") ) then takeanap() > because the latter needs to do extra property visits and string comparisons > and it is so indirect to express what I really want. > > I really dont care what the mathematical definition is unless you tell me > Drools is a math. engine rather than a rule engine to express business > requirements. That, I should update myself and take a step back to look at > Drools again. Just my own opinion :P > > > > > -- > View this message in context: http://drools.46999.n3.nabble.com/forall-is-satisfied-when-there-is-nothi... > Sent from the Drools: User forum mailing list archive at Nabble.com. > _______________________________________________ > rules-users mailing list > rules-users(a)lists.jboss.org > https://lists.jboss.org/mailman/listinfo/rules-users