Huh. That raises the question "Why doesn't clojure.lang.ITransientCollection extend clojure.lang.IEditableCollection, so the .asTransient method is idempotent?" Would that make a circular reference? --Leif
On Tuesday, March 20, 2012 3:32:28 PM UTC-7, Andy Fingerhut wrote: > > Sorry, I said something incorrect. into cannot take transients as the > first arg. It calls transient internally on the first arg for speed. This > does not modify the value you passed in at all -- it creates a new > transient data structure from what you pass in. > > If you try calling transient on a data structure that is already a > transient, you get an error. Thus this gives an error: > > user=> (def x [1 2 3]) > #'user/x > user=> (def tx (transient x)) > #'user/tx > user=> (into tx [5 6 7]) > ClassCastException clojure.lang.PersistentVector$TransientVector cannot be > cast to clojure.lang.IPersistentCollection clojure.core/conj (core.clj:83) > user=> (into x [5 6 7]) > [1 2 3 5 6 7] > > Andy > > > On Mar 20, 2012, at 11:30 AM, Andy Fingerhut wrote: > > func! (bang) is a naming convention from the programming language Scheme > that Clojure often uses. In general it means that the function mutates > data, i.e. it is not a pure function. Clojure does not have a ! after all > of its core functions that do this, but it does after some. In particular, > the functions that operate on transients like conj! assoc! persistent! etc. > mutate their arguments. > > Many (maybe most) regular collection functions do not take transients. As > I said, I think it is an accident, not by design, that 'into' can take a > transient as an argument. Originally it only took persistent collections > as arguments (perhaps also seqs, but those are immutable, too). > > Andy > > On Mar 20, 2012, at 11:17 AM, László Török wrote: > > Ok, > > so the pattern is: > > func! (bang) takes a transient and returns a transient > > regular collection functions MAY take a transient but ALWAYS return a > persistent collection, right? :) > > thx > Las > > 2012/3/20 Andy Fingerhut <andy.finger...@gmail.com> > >> into uses transient and persistent! for speed. The fact that into can >> take a transient as input is an accidental consequence of that, I think. >> Before into was changed to use transients internally, it could only take >> persistent data structures as input, and return a persistent data structure. >> >> Andy >> >> On Mar 20, 2012, at 10:32 AM, László Török wrote: >> >> Hi, >> >> While implementing qsort with clojure for fun, I thought about using >> transient vectors to speed up sorting vs the "naive" functional >> implementation. >> >> I need an *into!* version of *into *when joining two sorted subarrays >> and I was wondering why there isn't one. >> >> It seems that (source into) does in fact support a transient collection >> as the first argument, however it calls persistent! on the result. >> >> What was the rationale behind the decision? (Note: I'm not questioning >> it, just interested.) >> Is there a particular reason why this feature remains undocumented? >> >> -- >> László Török >> >> >> -- >> 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 > > > > > -- > László Török > > > -- > 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
