On 28 Jan 2010, at 18:41, Avdi Grimm wrote: > So just to be sure I understand this, this means that: > > ((color IN [] OR num_spots IN [5])) > > is *exactly* equivalent to: > > (num_spots IN [5]) > > Yes?
Yes, this actually follows from pretty straightforward math, if you look at things like set theory. Think of it as like "color is one of the elements in the empty set", which is always false since nothing is contained in the empty set. If you have a clause in a logical or that is always false, the result of the or clause is always the same as the result of the other clause. > Does this also mean that: > > ((NOT (color IN []) OR num_spots IN [5])) > > is exactly equivalent to (), i.e. "select all"? Since the first > alternative is the negation of a set that matches nothing. Yes, exactly. -- Dirkjan -- You received this message because you are subscribed to the Google Groups "DataMapper" group. To post to this group, send email to datamap...@googlegroups.com. To unsubscribe from this group, send email to datamapper+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/datamapper?hl=en.
