Interesting question. Here's something I whipped up in response: http://gist.github.com/355456
I intentionally provide only lazy-alter and no lazy-ref-set. The reason is that lazy-alter can be coded so that all the unwrapping and rewrapping of delays can be abstracted away from the user-provided transformation function. A lazy-ref-set function would impose a much stricter discipline on the user in order to maintain laziness. All the usual caveats about full laziness apply: beware of space leaks, delayed side effects, etc. -Per On Sun, Apr 4, 2010 at 9:35 PM, Bob Hutchison <hutch-li...@recursive.ca> wrote: > > Hi, > > I have a situation where: > 1) I have a lot of 'values' that are both expensive to compute and quite > large (they aren't all going to fit into memory) and most of which will not > be needed (this time, but maybe later) > 2) I may have a need to update several of them them (in a transaction) > > The first case looks to be perfectly suited to delays. The second to refs. > The values are going to be deftypes. > > So what I've come up with is a ref -> a delay -> a deftype. > > This is fine but it gets troublesome fast. > > The first time you try to get the deftype you have to write something like > @@my-thing, and you keep writing that until the value is updated. The update > will make the 'path' a ref -> a deftype (the delay is gone). This is bad I > think because you now have to write @my-thing to get the value. > > The best that I've come up with is to update the ref with another delay, kind > of like: (dosync (ref-set my-thing (delay my-updated-thing))) > > Is the the way to do it? Is there something better I could be doing? > Something deref-able that I'm missing that is better suited than delay? Some > kind of deref-all-the-way function? > > Thanks, > Bob > > > ---- > Bob Hutchison > Recursive Design Inc. > http://www.recursive.ca/ > weblog: http://xampl.com/so > > > > > -- > 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 > > To unsubscribe, reply using "remove me" as the subject. > -- 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
