2010/3/14 Meikel Brandmeyer <m...@kotka.de> > In short: ensure is used when you require only read access to a Ref, > but need the value to be constant through the transaction. If you > modify the a Ref via alter or ref-set, the ensure is not necessary. > > OK, I think I've finally figured out why I've always found ensure to be a bit confusing. I often see ensure described like you did above, that you use it if you "need the value to be constant through the transaction." I was puzzled, because I thought you were already guaranteed that the value is constant by the semantics promised by the STM system, "All reads of Refs will see a consistent snapshot of the 'Ref world' as of the starting point of the transaction (its 'read point')."
So what I'm finally realizing is that although you are guaranteed a consistent read value throughout the transaction, that value might become out of touch with "reality" unless you use ensure. So I think I get it now, although Michal's examples make no sense to me, so maybe I'm still missing something. -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en
