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

laune wrote > On 08/01/2014, Davide Sottara < > dsotty@ > > 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