It's in the official API documentation<http://clojure.github.com/clojure/branch-master/clojure.core-api.html#clojure.core/reduced>. Yes, it's new with Clojure 1.5.
On Friday, March 1, 2013 12:42:18 AM UTC+1, Geo wrote: > > I didn't know reduce could be short circuited! I assume from the code > below this is done calling the function reduced? Is this in Clojure 1.5 > only and is where is this documented? > > On Wednesday, February 27, 2013 4:59:33 AM UTC-5, Christophe Grand wrote: >> >> >> On Wed, Feb 27, 2013 at 10:21 AM, Marko Topolnik <marko.t...@gmail.com>wrote: >> >>> >>> (defn blank? [s] (every? #(Character/isWhitespace %) s)) >>>> >>>> Have you ever wondered about its performance? Here you go: >>>> >>>> user> (time (dotimes [_ 10000] (blank? " >>>> "))) >>>> "Elapsed time: 3887.578 msecs" >>>> >>> >>> To give a more complete picture, this version >>> >>> (defn blank? [s] (every? #(Character/isWhitespace ^char %) s)) >>> >>> is only six times slower than the expanded version, and keeping an eye >>> on reflection warnings is not such a drag. So, if it could be demonstrated >>> that in general the properly type-hinted, but otherwise idiomatic Clojure >>> is not more than 10 times slower than idiomatic Java, I'd consider that at >>> least a good starting point. >>> >> >> Now that reduce can be short-circuited, redifining every?, some and al on >> top of it would yield some interesting gains: >> >> (defn revery? [pred coll] >> (reduce (fn [t x] >> (if (pred x) >> t >> (reduced false))) true coll)) >> >> (defn rblank? [s] (revery? #(Character/isWhitespace ^char %) s)) >> (defn blank? [s] (every? #(Character/isWhitespace ^char %) s)) >> >> => (dotimes [_ 10] >> (time (dotimes [_ 100000] (blank? " >> ")))) >> "Elapsed time: 515.371 msecs" >> "Elapsed time: 500.408 msecs" >> "Elapsed time: 507.646 msecs" >> "Elapsed time: 644.074 msecs" >> "Elapsed time: 529.717 msecs" >> "Elapsed time: 482.813 msecs" >> "Elapsed time: 557.563 msecs" >> "Elapsed time: 486.573 msecs" >> "Elapsed time: 493.636 msecs" >> "Elapsed time: 481.357 msecs" >> nil >> => (dotimes [_ 10] >> (time (dotimes [_ 100000] (rblank? " >> ")))) >> "Elapsed time: 227.692 msecs" >> "Elapsed time: 99.937 msecs" >> "Elapsed time: 95.922 msecs" >> "Elapsed time: 91.193 msecs" >> "Elapsed time: 90.794 msecs" >> "Elapsed time: 94.765 msecs" >> "Elapsed time: 89.842 msecs" >> "Elapsed time: 120.551 msecs" >> "Elapsed time: 90.843 msecs" >> "Elapsed time: 93.523 msecs" >> nil >> >> Christophe >> > -- -- 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.
