Thank you for your answers. I think now I understand it. It makes sense that it's a maker interface. I was confused from the fact that List supports O(1) but it is, of course, possible in actual implementations.
Regards. Keisuke On Wed, Aug 5, 2015 at 5:40 AM, Raymond Huang <12ay.hu...@gmail.com> wrote: > That sounds about right. > > See > https://github.com/clojure/clojure/blob/41af6b24dd5be8bd62dc2b463bc53b55e18cd1e5/src/jvm/clojure/lang/Counted.java > > On Tue, Aug 4, 2015 at 11:06 AM, Gary Verhaegen <gary.verhae...@gmail.com> > wrote: > >> I don't know of it is correct, but I also remember reading that Counted >> was a "marker interface", i.e. it does not actually add any method but it >> implies that the count operation will be "fast". >> >> >> On Tuesday, 4 August 2015, Laurent PETIT <laurent.pe...@gmail.com> wrote: >> >>> If I'm remember correctly, the Counted interface must only be >>> implemented by collection implementations for which it is guaranteed that >>> count() is an O(~1) operation >>> >>> 2015-08-04 17:07 GMT+02:00 Keisuke Fukuda <keisukefuk...@gmail.com>: >>> >>>> Hello, >>>> >>>> I've been investigating the basic data structures and their underlying >>>> concepts in Clojure, particularly focusing on the definitions of coll, seq, >>>> map, vector, set, etc. and their inclusion relationships. >>>> >>>> I saw a Venn diagram in this page[1]. Although it is as of Clojure 1.3, >>>> I confirmed it is still correct. "Counted" interface has its only method >>>> count() and it implies that we can get the explicit size of a "Counted" >>>> collection. >>>> >>>> However, IPersistentCollection, which is actually the definition of >>>> collections, also has count() method. It's a bit surprising to me that even >>>> LazySeq supports count() (indirectly via ISeq). >>>> >>>> Questions: >>>> If IPersistentCollection has count() method, What is "Counted" for? >>>> Is it always reasonable for LazySeq to support count() method? >>>> Shouldn't there be an explicit "CountedLazySeq", >>>> >>>> Thanks. >>>> Keisuke >>>> >>>> [1] http://www.brainonfire.net/files/seqs-and-colls/main.html >>>> >>>> >>>> -- >>>> FUKUDA, Keisuke <福田圭祐> >>>> Tokyo, Japan >>>> Email: keisukefuk...@gmail.com >>>> >>>> -- >>>> 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/d/optout. >>>> >>> >>> >>> >>> -- >>> Laurent Petit >>> >>> -- >>> 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/d/optout. >>> >> -- >> 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/d/optout. >> > > -- > 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/d/optout. > -- FUKUDA, Keisuke <福田圭祐> Tokyo, Japan Email: keisukefuk...@gmail.com -- 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/d/optout.
