Thank you very very much Jan .... idiomatic is what I need to learn :) Regards, Kashyap
On Tuesday, January 14, 2014 12:47:19 AM UTC+5:30, Jan Herich wrote: > > As Mauricio already mentioned, map is not meant to be used for > side-effects, if you want to need to evaluate a sequence for side-effects, > use doseq <http://clojuredocs.org/clojure_core/clojure.core/doseq>instead. > Regarding your first question about explicit loop-recur, i think it's > reasonable way to write the functionality you want to achieve, even if the > for macro is maybe > little more idiomatic and shorter/more concise, here is the comparison: > > (def url-sequence (map #(str "http://www.mysite.com/list.php?pageID="; %) > (range))) > > (def download > (loop [urls url-sequence lst []] > (let [u (first urls) > r (rest urls) > resp (client/get u) > next (re-find #"(s?)title=\"next page\">Next >>" (:body resp)) > segments ((html2data (:body resp)) :segment) > data (map segment2data segments)] > (if next > (recur r (conj lst data)) > (conj lst data))))) > > (def download > (->> (for [url url-sequence > :let [body (:body (client/get url)) > next-pages (re-find #"(s?)title=\"next page\">Next > >>" body)] > :while next-pages] > (map segment2data (-> body (html2data) :segment)))) > (into [])) > > Also note that i didn't use local binding named next, but instead i named it > next-pages, because next > local name could lead to surprise if you forget that you aliased something to > next and try to use clojure > core next function :) > > > Dňa pondelok, 13. januára 2014 15:49:50 UTC+1 Kashyap CK napísal(-a): >> >> Hi, >> I've been dabbling with Clojure for a bit and I am really loving it!!! >> >> I am trying to write a clojure program to download a bunch of URLs and I >> was wondering what is the right way to do it - >> My current implementation is as follows >> >> (def url-sequence (map #(str "http://www.mysite.com/list.php?pageID="; %) >> (range))) >> >> (def download >> (loop [urls url-sequence lst []] >> (let >> [ >> u (first urls) >> r (rest urls) >> resp (client/get u) >> next (re-find #"(s?)title=\"next page\">Next >>" (:body >> resp)) >> segments ((html2data (:body resp)) :segment) >> data (map segment2data segments) >> ] >> (if next >> (recur r (conj lst data)) >> (conj lst data))))) >> >> I was wondering if I could replace the loop thingy with a map - that is >> when I experimented with a simple piece of code and found something that >> was not intuitive. >> I'd really appreciate it if someone could tell me what's going on when I >> do the following - >> >> user> (defn xx [] (map println [1 2 3 4 5 6])) >> #'user/xx >> user> (take 2 (xx)) >> (1 >> 2 >> 3 >> 4 >> 5 >> 6 >> nil nil) >> user> >> >> Regards, >> Kashyap >> > -- -- 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.
