Re: Why does (conj (transient {}) {}) fail with CCE?
you must use conj! instead of conj.
在 2012-8-9 PM8:49，Jacek Laskowski ja...@japila.pl写道：
Hi,
I've been digging into the sources of Clojure and found frequencies.
There's the transient function and I thought I'd use it with a map and
conj. Why does this fail?
user= (conj {} {:y 1})
{:y 1}
user= (conj (transient {}) {:y 1})
ClassCastException [trace missing]
I ran into the issue before and got a more comprehensible exception.
ClassCastException clojure.lang.PersistentArrayMap$TransientArrayMap
cannot be cast to clojure.lang.IPersistentCollection
clojure.core/conj (core.clj:83)
I can't explain why the exception is reported in two different versions.
Should the exception be thrown? What's the rationale behind
TransientArrayMap *not* being a IPersistentCollection?
Jacek
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Jacek Laskowski
Functional languages (Clojure), Java EE, and IBM WebSphere -
http://blog.japila.pl
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slow. Plato
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Re: Why does (conj (transient {}) {}) fail with CCE?
On Thu, Aug 9, 2012 at 6:19 PM, Jacek Laskowski ja...@japila.pl wrote: What's the rationale behind TransientArrayMap *not* being a IPersistentCollection? A transient map can't be a persistent map at the same time. You need to use the transient version of conj, called conj! to conjoin something into a transient map and then use persistent! to get a persistent version back. Please read the documentation for more background http://clojure.org/Transients Regards, BG -- Baishampayan Ghose b.ghose at 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
Re: Why does (conj (transient {}) {}) fail with CCE?
On Thu, Aug 9, 2012 at 2:54 PM, Baishampayan Ghose b.gh...@gmail.com wrote: A transient map can't be a persistent map at the same time. You need to use the transient version of conj, called conj! to conjoin something into a transient map and then use persistent! to get a persistent version back. Please read the documentation for more background http://clojure.org/Transients Thanks! It's so much clearer now. Jacek -- Jacek Laskowski Functional languages (Clojure), Java EE, and IBM WebSphere - http://blog.japila.pl Never discourage anyone who continually makes progress, no matter how slow. Plato -- 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
