And this is exactly as it should be. The sorted set has no way to compare items other than by your comparator. If it just arbitrarily decided to use = instead of checking that (zero? (compare x y)) it would not be using your comparator.
Note also that the behavior of contains? is consistent with conj and disj: if the item is contained in the set, then conj will keep size the same and disj will decrease it; otherwise conj will increase the size and disj will leave it the same. On Mar 15, 3:39 pm, Stuart Campbell <stu...@harto.org> wrote: > Actually, sorted-map-by does behave the same way, but in your example you > tried to lookup a value instead of a key: > > user> (def m (sorted-map-by #(< (%1 0) (%2 0)) [1 :a] [2 :b])) > #'user/m > user> (get m [1 :foo]) > [2 :b] > > It looks like > PersistentTreeMap.entryAt<https://github.com/clojure/clojure/blob/master/src/jvm/clojure/lang/P...>is > responsible for this behaviour. > > Regards, > Stuart > > On 13 March 2012 05:20, mnicky <markus.mas...@gmail.com> wrote: > > > It seems that when using the sorted set with my own comparator > > (sorted-set-by), > > the lookup via 'contains?' function is based only on the part of the items > > that participate in the ordering: > > > (contains? (sorted-set [1 :a] [2 :b]) [2 :c]) > > ;=> false > > > (contains? (sorted-set-by #(< (%1 0) (%2 0)) [1 :a] [2 :b]) [2 :c]) > > ;=> true > > > The documentation of 'sorted-set-by' says that the _whole_ items are keys: > > > (doc sorted-set-by) > > ; clojure.core/sorted-set-by > > ; ([comparator & keys]) > > ; Returns a new sorted set with supplied keys, using the supplied > > comparator. > > ; nil > > > So according to the documentation of 'contains?', it should do lookup > > based on the whole items, not just their parts used in the comparator: > > > (doc contains?) > > ; clojure.core/contains? > > ; ([coll key]) > > ; Returns true if key is present in the given collection, otherwise > > ; returns false. Note that for numerically indexed collections like > > ; vectors and Java arrays, this tests if the numeric key is within the > > ; range of indexes. 'contains?' operates constant or logarithmic time; > > ; it will not perform a linear search for a value. See also 'some'. > > ; nil > > > It's also worth noting that 'sorted-map-by' doesn't behave in this way: > > > (contains? (sorted-map-by #(< (%1 0) (%2 0)) [1 :a] [2 :b]) [2 :c]) > > ;=> false > > > Can this be a bug? If not, what's the reason behind this behavior? > > > -- Mnicky > > > -- > > 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 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
