Re: find first match in a sequence
I'm glad you pointed this out! On stackoverflow everyone was assuming filter was completely lazy in all cases On Sunday, May 19, 2013 at 4:54:53 PM UTC+2, Jim foo.bar wrote: > > ha! you cheated with iterate... > > try this which is closer to the example... > > (first (filter odd? (map #(do (println "realized " %) %) [2 4 6 7 8 9]))) > realized 2 > realized 4 > realized 6 > realized 7 > realized 8 > realized 9 > 7 > > Jim > > > > On 19/05/13 15:31, Cedric Greevey wrote: > > On Sun, May 19, 2013 at 10:06 AM, Jim - FooBar(); > wrote: > >> no need to traverse the entire seq with 'filter' if you only want the 1st >> match... >> > > Pretty sure filter is lazy. > > user=> (first (filter odd? (map #(do (println "realized " %) %) (iterate > inc 0 > realized 0 > realized 1 > 1 > user=> > > -- > -- > You received this message because you are subscribed to the Google > Groups "Clojure" group. > To post to this group, send email to clo...@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+u...@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+u...@googlegroups.com . > For more options, visit https://groups.google.com/groups/opt_out. > > > > > -- 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/d/optout.
Re: find first match in a sequence
On Sun, May 19, 2013 at 4:54 PM, Jim - FooBar(); wrote: > ha! you cheated with iterate... > > try this which is closer to the example... > > (first (filter odd? (map #(do (println "realized " %) %) [2 4 6 7 8 9]))) > realized 2 > realized 4 > realized 6 > realized 7 > realized 8 > realized 9 > 7 > > Jim > => (some #(when (odd? %) %) (map #(do (println "realized" %) %) [2 4 6 7 8 9])) realized 2 realized 4 realized 6 realized 7 realized 8 realized 9 7 ;) In fact, just calling 'first' on a mapped sequence gives the same behaviour: => (first (map #(do (println "realized" %) %) [2 4 6 7 8 9])) realized 2 realized 4 realized 6 realized 7 realized 8 realized 9 2 That said, 'some' does avoid realizing the first 32 elements if it's a vec. I still don't think you should care about that though - that's kind of the point of laziness, to be able to use map/filter etc without caring about how much is realized. Jonathan -- -- 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.
Re: find first match in a sequence
On Wednesday, 11 February 2009 00:18:53 UTC+8, Jeff Rose wrote: > Hi, > Is there a built-in function that will return the first item in a > collection that matches a predicate? (Something equivalent to Ruby's > Enumerable#find...) Seems pretty basic, but I can't find it in the docs. > > Thanks, > Jeff > See the find-first function in my cljutils library: https://github.com/mikera/clojure-utils/blob/master/src/main/clojure/mikera/cljutils/find.clj Note the initial check to see if the collection is Indexed: if it is then it is better to search by index than to create a seq (which causes a lot of unnecessary allocations) -- -- 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.
Re: find first match in a sequence
remember the 32-chunked model... :) Jim On 19/05/13 15:54, Jim - FooBar(); wrote: ha! you cheated with iterate... try this which is closer to the example... (first (filter odd? (map #(do (println "realized " %) %) [2 4 6 7 8 9]))) realized 2 realized 4 realized 6 realized 7 realized 8 realized 9 7 Jim On 19/05/13 15:31, Cedric Greevey wrote: On Sun, May 19, 2013 at 10:06 AM, Jim - FooBar(); mailto:jimpil1...@gmail.com>> wrote: no need to traverse the entire seq with 'filter' if you only want the 1st match... Pretty sure filter is lazy. user=> (first (filter odd? (map #(do (println "realized " %) %) (iterate inc 0 realized 0 realized 1 1 user=> -- -- 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. -- -- 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.
Re: find first match in a sequence
ha! you cheated with iterate... try this which is closer to the example... (first (filter odd? (map #(do (println "realized " %) %) [2 4 6 7 8 9]))) realized 2 realized 4 realized 6 realized 7 realized 8 realized 9 7 Jim On 19/05/13 15:31, Cedric Greevey wrote: On Sun, May 19, 2013 at 10:06 AM, Jim - FooBar(); mailto:jimpil1...@gmail.com>> wrote: no need to traverse the entire seq with 'filter' if you only want the 1st match... Pretty sure filter is lazy. user=> (first (filter odd? (map #(do (println "realized " %) %) (iterate inc 0 realized 0 realized 1 1 user=> -- -- 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. -- -- 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.
Re: find first match in a sequence
On Sun, May 19, 2013 at 10:06 AM, Jim - FooBar(); wrote: > no need to traverse the entire seq with 'filter' if you only want the > 1st match... > Pretty sure filter is lazy. user=> (first (filter odd? (map #(do (println "realized " %) %) (iterate inc 0 realized 0 realized 1 1 user=> -- -- 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.
Re: find first match in a sequence
Try this user> (first (drop-while even? [2 4 6 7 8 10])) 7 19.05.2013, 23:06, "Jim - FooBar();" : > no need to traverse the entire seq with 'filter' if you only want the 1st > match... > > (some #(when (odd? %) %) [2 4 6 7 8 9]) > => 7 > > Jim > > On 19/05/13 13:42, Thumbnail wrote: > >> ... or just (comp first filter) > >>> ((comp first filter) odd? [2 4 6 7 8 9]) >>> >>> => 7 >> >> -- >> -- >> 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. > > -- > -- > 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. -- -- 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.
Re: find first match in a sequence
no need to traverse the entire seq with 'filter' if you only want the 1st match... (some #(when (odd? %) %) [2 4 6 7 8 9]) => 7 Jim On 19/05/13 13:42, Thumbnail wrote: ... or just (comp first filter) ((comp first filter) odd? [2 4 6 7 8 9]) => 7 -- -- 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. -- -- 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.
Re: find first match in a sequence
... or just (comp first filter) ((comp first filter) odd? [2 4 6 7 8 9]) => 7 -- -- 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.
Re: find first match in a sequence
Hi, Am 10.02.2009 um 18:00 schrieb Jeff Rose: Oh cool! I hadn't thought about this aspect of laziness before. I can see there is some zen here that is worth exploring... Many ways to Rome: (first (drop-while (complement predicate) coll)) :) Sincerely Meikel smime.p7s Description: S/MIME cryptographic signature
Re: find first match in a sequence
Oh cool! I hadn't thought about this aspect of laziness before. I can see there is some zen here that is worth exploring... Thanks Mark and Stuart. -Jeff Mark Fredrickson wrote: > Filter is lazy: > > http://clojure.org/api#toc228 > > So you can implement find-first as (first (filter pred coll)) > > -M > > On Feb 10, 2009, at 10:19 AM, Jeff Rose wrote: > > >> Well, in case someone else needs the same function and it isn't built- >> in, here's what I'm using in the meantime. (Based off of the some >> function that comes in core...) >> >> (defn find-first [pred coll] >> (when (seq coll) >>(if (pred (first coll)) >> (first coll) >> (recur pred (rest coll) >> >> Cheers, >> Jeff >> >> On Feb 10, 5:18 pm, Jeff Rose wrote: >> >>> Hi, >>> Is there a built-in function that will return thefirstitemin a >>> collection that matches a predicate? (Something equivalent to Ruby's >>> Enumerable#find...) Seems pretty basic, but I can'tfindit in the >>> docs. >>> >>> Thanks, >>> Jeff >>> >>> > > - Mark Fredrickson > mark.m.fredrick...@gmail.com > http://www.markmfredrickson.com > > > > > > > > > > --~--~-~--~~~---~--~~ 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 -~--~~~~--~~--~--~---
Re: find first match in a sequence
On Feb 10, 11:18 am, Jeff Rose wrote: > Is there a built-in function that will return the first item in a > collection that matches a predicate? (Something equivalent to Ruby's > Enumerable#find...) Seems pretty basic, but I can't find it in the docs. Hi, Jeff, here's how I do it: user> (def numbers [2 4 6 7 8 9]) #'user/numbers user> (some #(when (odd? %) %) numbers) 7 -Stuart Sierra --~--~-~--~~~---~--~~ 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 -~--~~~~--~~--~--~---
Re: find first match in a sequence
Filter is lazy: http://clojure.org/api#toc228 So you can implement find-first as (first (filter pred coll)) -M On Feb 10, 2009, at 10:19 AM, Jeff Rose wrote: > > Well, in case someone else needs the same function and it isn't built- > in, here's what I'm using in the meantime. (Based off of the some > function that comes in core...) > > (defn find-first [pred coll] > (when (seq coll) >(if (pred (first coll)) > (first coll) > (recur pred (rest coll) > > Cheers, > Jeff > > On Feb 10, 5:18 pm, Jeff Rose wrote: >> Hi, >> Is there a built-in function that will return thefirstitemin a >> collection that matches a predicate? (Something equivalent to Ruby's >> Enumerable#find...) Seems pretty basic, but I can'tfindit in the >> docs. >> >> Thanks, >> Jeff > > - Mark Fredrickson mark.m.fredrick...@gmail.com http://www.markmfredrickson.com --~--~-~--~~~---~--~~ 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 -~--~~~~--~~--~--~---
Re: find first match in a sequence
Well, in case someone else needs the same function and it isn't built- in, here's what I'm using in the meantime. (Based off of the some function that comes in core...) (defn find-first [pred coll] (when (seq coll) (if (pred (first coll)) (first coll) (recur pred (rest coll) Cheers, Jeff On Feb 10, 5:18 pm, Jeff Rose wrote: > Hi, > Is there a built-in function that will return thefirstitemin a > collection that matches a predicate? (Something equivalent to Ruby's > Enumerable#find...) Seems pretty basic, but I can'tfindit in the docs. > > Thanks, > Jeff --~--~-~--~~~---~--~~ 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 -~--~~~~--~~--~--~---
find first match in a sequence
Hi, Is there a built-in function that will return the first item in a collection that matches a predicate? (Something equivalent to Ruby's Enumerable#find...) Seems pretty basic, but I can't find it in the docs. Thanks, Jeff --~--~-~--~~~---~--~~ 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 -~--~~~~--~~--~--~---
