Thanks for the pointers. I was indeed able to make it work with dorun. ;) Still, I'm not sure I understand what all the fuss is about regarding laziness. I'll take your word for it for now but I hope to grock it eventually.
Thanks! Max On Mar 2, 12:30 am, David Nolen <dnolen.li...@gmail.com> wrote: > Remember that you can force lazy sequences if you need to as you are with > doseq with doall (retains head) and dorun (does not) as well. > You probably want > > (dorun (map #(add-watch % watcher callback-fn) all-agents)) > > I think it's pretty clear here what's going on. Your code needs > side-effects. In Clojure side-effect code tends to stands out. > > I sympathize with your frustration, I remember getting excited about Lisp > macros but spending many many long hours trying to understand how to write > even a simple one. > > Similarly I think lazy sequences are worth the initial frustration ;) > > On Mon, Mar 2, 2009 at 12:06 AM, max3000 <maxime.lar...@gmail.com> wrote: > > > Hi, > > > I find the laziness in clojure very hard to wrap my head around. I > > understand the idea and it's probably nice in theory. However, in real > > life it doesn't seem really useful beyond hardcore mathematical > > problems. > > > Case in point, I just spent 2 hours debugging a piece of code (shown > > below) that seemed simple enough. This is the 3rd time this week that > > I've lost substantial time to laziness. I'm pretty pissed to tell the > > truth and I find myself wrapping things in doseq more and more just to > > be sure. I rarely use 'for' anymore, what's the point? > > > Here is the code that gave me trouble: > > > (map #(add-watch % watcher callback-fn) all-agents) > > > This was not executing. I had to change it to the below expression: > > > (doseq [agent all-labor-agents] > > (add-watch agent total-labor-agent callback-fn)) > > > This second expression seems less elegant than the map above. Why > > doesn't clojure realize that an add-watch really should actually loop > > over all-agents? Why is it that Java calls are not made in similar > > expressions? > > > Is laziness so useful that we should waste time investigating and > > fixing errors like this? Sure, there could be special constructs for > > laziness when we really need it. However, clojure shouldn't default to > > it IMO. At this point, laziness is a nice concept but it feels > > somewhat removed from reality to tell the truth. Of course I want to > > iterate over my collection when I'm doing an add-watch! > > > What am I missing? > > > Thanks, > > > Max --~--~---------~--~----~------------~-------~--~----~ 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 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 -~----------~----~----~----~------~----~------~--~---
