Hi, another hint that you can rely on sorted maps returning sorted keys and seqis the behavior of Sorted Map in Java 7
HTH -Gianluca On Sunday, October 20, 2013 4:10:53 PM UTC+2, juan.facorro wrote: > > Hi Ru, > > I hope I understood your question correctly, because I did some digging > based on that, since I was curious about the answer. > > ** > The implementation for sorted maps (at least in 1.5.1 and as far back as > 1.2.0, > maybe farther, I didn't check) guarantees that the result from from *keys* > will > return an ascending sorted seq of keys; *vals* will return a seq > following the corresponding keys order. Having said that, the docstring for > *keys* doesn't mention anything about the order of the elements in the > sequence, so the order could considered as an implementation detail... on > the other hand it hasn't changed in quite a while so if it were me I would > consider it a feature, plus the documentation on sorted maps > here<http://clojure.org/data_structures>, > says: > > [...] > seq<http://clojure.github.com/clojure/clojure.core-api.html#clojure.core/seq>returns > a sequence of map entries, which are key/value pairs. Sorted map >> also supports >> rseq<http://clojure.github.com/clojure/clojure.core-api.html#clojure.core/rseq>, >> >> which returns the entries in reverse order. [...] > > > Which implicitly suggests (at least for me) that *seq* returns the > entries in order (since *rseq* returns the inverse, but *only* for sorted > maps). > > Hope it helps > > --------- > > Digging details: > > *vals* is implemented in terms of* > clojure.lang.RT.vals()<https://github.com/clojure/clojure/blob/clojure-1.5.1/src/jvm/clojure/lang/RT.java#L518> > * (*keys* follows the same approach). There, the map is *seq*'ed and that > is what is used in > *APersistentMap.ValSeq*<https://github.com/clojure/clojure/blob/clojure-1.5.1/src/jvm/clojure/lang/APersistentMap.java#L164> > 's (and > *APersistentMap.KeySeq*<https://github.com/clojure/clojure/blob/clojure-1.5.1/src/jvm/clojure/lang/APersistentMap.java#L133> > 's) implementation of *first* and *next* to return the values. The > sequence of entries as a result from *(seq m)** *determines the order of > the keys *and* values in the seqs returned from the functions. This means > that if entries are sorted by their keys, then the corresponding values > will follow the same order with vals,* *that is, they won't be > necessarily ordered. > > The *seq* of a *sorted-map* is guaranteed to return entries ordered by * > key*, based on the implementation of > *entrySet()*<https://github.com/clojure/clojure/blob/clojure-1.5.1/src/jvm/clojure/lang/APersistentMap.java#L214> > (from > *APersitentMap*) and the > *iterator()*<https://github.com/clojure/clojure/blob/clojure-1.5.1/src/jvm/clojure/lang/PersistentTreeMap.java#L204> > and > *NodeIterator*<https://github.com/clojure/clojure/blob/clojure-1.5.1/src/jvm/clojure/lang/PersistentTreeMap.java#L836>(from > > *PersistentTreeMap*, class with which sorted maps are implemented). > > Juan > > On Sunday, October 20, 2013 8:25:02 PM UTC+8, ru wrote: >> >> Dear clojure people! >> >> Do results of functions "keys" and "vals" ordered for sorted maps >> accordingly? Does it guaranteed? >> >> Thanks in advance. >> >> Sincerely, >> Ru >> > -- -- 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.
