Thanks for the explanations! So is there a way to build a set or map that has sorting property independent from the element lookup?
On Friday, March 16, 2012 2:03:15 AM UTC+1, Alan Malloy wrote: > > 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..<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+unsubscribe@googlegroups.com<clojure%2bunsubscr...@googlegroups.com> > > > > > > For more options, visit this group at > > >http://groups.google.com/group/clojure?hl=en<http://groups.google.com/group/clojure?hl=en> On Friday, March 16, 2012 2:03:15 AM UTC+1, Alan Malloy wrote: > > 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..<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+unsubscribe@googlegroups.com<clojure%2bunsubscr...@googlegroups.com> > > > > > > For more options, visit this group at > > >http://groups.google.com/group/clojure?hl=en<http://groups.google.com/group/clojure?hl=en> On Friday, March 16, 2012 2:03:15 AM UTC+1, Alan Malloy wrote: > > 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..<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+unsubscribe@googlegroups.com<clojure%2bunsubscr...@googlegroups.com> > > > > > > For more options, visit this group at > > >http://groups.google.com/group/clojure?hl=en<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
