2009/3/3 Meikel Brandmeyer <m...@kotka.de> > Hi, > > Am 03.03.2009 um 16:42 schrieb Chouser: > > If you have a lazy sequence with side-effects, you almost certainly >> don't want to let it out of your sight. You're likely to get very >> strange behavior unless you're exceedingly careful. Most likely, if >> you've got a lazy seq with side effects you should force it with dorun >> or doall immediately. Use doall if you care about the values in the >> produced seq, otherwise use dorun. >> >> This means that dorun should almost always show up right next to the >> form producing the lazy seq, which means doseq is very likely a better >> choice, as it is more efficient and usually more succinct than dorun >> combined with a lazy-seq producer. >> > > What is the use case for dorun? It returns nil, so it can itself only > be called as a side-effect. From doall and dorun, only doall makes > sense to me. It is either called immediately > > (doall (map ...)) > > Or when giving the seq out of the hands: > > (with-some resource > ... > (doall the-seq)) > > Why should there ever be the need to call dorun?
If you still want to force a veeerry long seq for side effect, without fearing to face an OutOfMemory error ? > > And by the way: the output of the following code doesn't lie. > > (let [the-seq (map #(* % 2) (range 100))] > (doseq [x the-seq] > (println "Just produced:" x))) > > 'for' is in rather a different category, since unlike the others it >> produces a lazy seq rather than forcing anything. Use 'for' when it's >> a more convenient way to express the lazy seq you want than the >> equivalent combination of map, filter, take-while, etc. >> > > I must confess, I almost never used for... Maybe I should > try to use it more often. > > Sincerely > Meikel > > --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
