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.
