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
>
> --
> 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
>
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