This is one of the most frequenly-asked questions and a source of surprise to practically every new Clojure user. An update to the official documentation on lazy sequences would surely help a lot here.
-marko On Sunday, March 17, 2013 9:18:05 AM UTC+1, Evan Mezeske wrote: > > I'd guess that what you're seeing is related to chunked sequences: > http://blog.fogus.me/2010/01/22/de-chunkifying-sequences-in-clojure/ . > > On Sunday, March 17, 2013 1:12:17 AM UTC-7, bruce li wrote: >> >> Hello, everyone. I'm writing some code that utilizes the lazy sequence. >> But I found something strange. Here is how: >> >> The code is like: >> >> (first (filter some-expensive-io urls)) >> >> The code is aimed to find the first result of the operations on the urls >> that is not nil. However, it seems that the io operations are executed once >> more than needed. As the operations are slow, one more round increases the >> overhead dramatically. >> >> Then I tested other pieces of code, such as: >> >> (first (filter #(when (> % 1) (println %) %) (range))) >> >> It prints out: >> 2 >> 3 >> 4 >> 5 >> 6 >> 7 >> 8 >> 9 >> 10 >> 11 >> 12 >> 13 >> 14 >> 15 >> 16 >> 17 >> 18 >> 19 >> 20 >> 21 >> 22 >> 23 >> 24 >> 25 >> 26 >> 27 >> 28 >> 29 >> 30 >> 31 >> >> and returns: 2 >> >> So why the lazy sequence is realized more than it is needed? Could I >> enforce the laziness and save unnecessary operation? >> >> >> Thanks, >> Bruce Li >> > -- -- 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 --- You received this message because you are subscribed to the Google Groups "Clojure" group. To unsubscribe from this group and stop receiving emails from it, send an email to clojure+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out.
