Thanks Leif, thanks folks, these are good tips.
On Mon, Nov 18, 2013 at 4:12 AM, Leif <leif.poor...@gmail.com> wrote: > > Hi, Alexandru. > > If you just need more performance on vectors only, there are the core > functions mapv, filterv, and subvec (O(1), which can be used to implement > takev and dropv). Also, looking at the source of mapv and filterv is > instructive, because they use transients internally; you might do that in > your solution to get a bit more speed. > > If you really need a generic solution where most clj.core functions are > performant on your custom data structures, I don't have suggestions, but > you can refer to what the experts do: > > https://github.com/clojure/data.priority-map > https://github.com/ztellman?tab=repositories (potemkin, clj-tuple, > immutable-bitset, et al) > > Hope that helps, > Leif > > > On Saturday, November 16, 2013 7:01:14 PM UTC-5, Alexandru Nedelcu wrote: >> >> Hi, >> >> I'm trying to understand the design of Clojure's collections and one >> thing that I find odd is the return of functions operating on sequences. >> Like for instance a call such as this will return a lazy-seq and not a >> vector: >> >> (drop 2 [1 2 3 4]) >> >> The reason why I find it odd is that data-structures have different >> characteristics and one may want to use a vector because it supports >> efficient indexing and appending to the end. >> >> Of course, dropping 2 elements like above from a vector is probably >> going to have O(n) complexity and thus returning something lazy is more >> appropriate. And while there are some operations, like "conj", "pop" and >> "peek" that preserve the type, functions such as map and filter also >> return lazy-seq. And I worry that the property of the collection you >> start with is lost, given that this returns a "cons": >> >> (conj (filter even? [1 2 3 4 5]) 6) >> >> So lets say that I want to write a generic function that preserves the >> type of that collection. Is something like this idiomatic? >> >> (defn only-evens [coll] >> (into (empty coll) (filter even? coll))) >> >> Thanks, >> >> -- >> Alexandru Nedelcu >> www.bionicspirit.com >> >> PGP Public Key: >> https://bionicspirit.com/key.aexpk >> >> -- > -- > 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. > -- Alexandru Nedelcu www.bionicspirit.com PGP Public Key: https://bionicspirit.com/key.aexpk -- -- 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.
