Thanks,you are right.I want to creat a map which keeps elements in insertion order, but clojure doesn‘t have. 在 2013-6-6 下午10:02，"Andy Fingerhut" <andy.finger...@gmail.com>写道：
> Your comparator #(if (= %1 %2) 0 1) may happen to give the correct answers > for your example sorted-maps, but it is also a bad comparator that will > fail for larger examples: > > user=> (:a (sorted-map-by #(if (= %1 %2) 0 1) :z -26 :b 1 :a 2 :c 3 :m 13 > :h 8)) > nil > user=> (:z (sorted-map-by #(if (= %1 %2) 0 1) :z -26 :b 1 :a 2 :c 3 :m 13 > :h 8)) > nil > > That is because if two items are not =, by returning 1 you are telling the > caller "the first argument should come after the second argument". Thus if > at some time the comparator is called as (cmp :a :z), and later it is > called as (cmp :z :a), it returns the inconsistent results that :a should > come after :z, and later that :z should come after :a. No sorted tree can > hope to return correct results given such an inconsistent comparator. > > More examples and discussion at the link below, if you are interested: > > > https://github.com/jafingerhut/thalia/blob/master/doc/other-topics/comparators.md > > Andy > > > On Thu, Jun 6, 2013 at 4:19 AM, dennis zhuang <killme2...@gmail.com>wrote: > >> Sorry, it's my mistake. >> Because treep map use the comparator to compare keys, and if the >> comparator returns 1 constantly,it can not find the item that equals the >> key. >> >> So i can modified the example,and it works: >> >> user=> (sorted-map-by #(if (= %1 %2) 0 1) :b 1 :a 2) >> {:b 1, :a 2} >> user=> (:a (sorted-map-by #(if (= %1 %2) 0 1) :b 1 :a 2)) >> 2 >> user=> (:b (sorted-map-by #(if (= %1 %2) 0 1) :b 1 :a 2)) >> 1 >> >> >> 2013/6/6 dennis zhuang <killme2...@gmail.com> >> >>> user=> (sorted-map-by (constantly 1) :b 1 :a 2) >>> {:b 1, :a 2} >>> user=> (:a (sorted-map-by (constantly 1) :b 1 :a 2)) >>> nil >>> user=> (keys (sorted-map-by (constantly 1) :b 1 :a 2)) >>> (:b :a) >>> user=> (count (sorted-map-by (constantly 1) :b 1 :a 2)) >>> 2 >>> user=> (:a (sorted-map-by (constantly 1) :b 1 :a 2)) >>> nil >>> >>> It looks so strange.The result map has keys :a and :b,but i can't get >>> their values. >>> Why? I try to hack the code,but i can't find the reason. >>> >>> >>> -- >>> 庄晓丹 >>> Email: killme2...@gmail.com xzhu...@avos.com >>> Site: http://fnil.net >>> Twitter: @killme2008 >>> >>> >>> >> >> >> -- >> 庄晓丹 >> Email: killme2...@gmail.com xzhu...@avos.com >> Site: http://fnil.net >> Twitter: @killme2008 >> >> >> -- >> -- >> 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.
