it is expected behavior, because update-in calls the supplied function with
the value it finds in the map as the first argument, so your first call
ends up being
(remove [1 2 3] #{2})
Since ([1 2 3] 2) = 3 and is truthy, the result is ().
In your second case you're using (partial remove #{2}), so the result is
'(1 3), which is then turned into a vector by vec.
On Thu, May 29, 2014 at 10:00 AM, Stuart Fehr <stuart.f...@gmail.com> wrote:
> I am not sure if this is considered a "bug" or if it is simply expected
> behavior, so I thought I would ask the list for clarification.
>
> I have this test which passes and shows the strange behavior that I am
> encountering:
>
> (deftest update-in-and-remove
> ;; The leaf value becomes and empty list instead of [1 3]
> (is (= {:mykey {:myotherkey '()}}
> (update-in {:mykey {:myotherkey [1 2 3]}} [:mykey :myotherkey]
> remove #{2})))
> ;; Forcing a vector results in the behavior that I would expect
> (is (= {:mykey {:myotherkey [1 3]}}
> (update-in {:mykey {:myotherkey [1 2 3]}} [:mykey :myotherkey]
> (comp vec (partial remove #{2}))))))
>
> I think this behavior is due to the use of apply in the definition of
> update-in and I think (but haven't tested) adding a partial to the
> non-recursive clause will fix this:
>
> https://github.com/clojure/clojure/blob/master/src/clj/clojure/core.clj#L5687
>
> However, I don't want to submit a "fix" if this is the expected behavior.
> Thoughts?
>
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