samppi <rbysam...@gmail.com> writes:
> with-meta's behavior is annoying for me. I often have something like
> this:
>
> (defn a [blah] (with-meta blah {:type ::incredible}))
> (defn b [foo] (with-meta (a foo) {::b 2}))
>
> I'd like ^(b []) to be {:type ::incredible, ::b 2}. But with-meta
> overwrites the metadata from a completely. Is there a standard
> function in core or contrib that does:
> (defn add-meta [obj obj-meta]
> (with-meta obj (into (meta obj) obj-meta)))
I think what you want is vary-meta:
user> (doc vary-meta)
-------------------------
clojure.core/vary-meta
([obj f & args])
Returns an object of the same type and value as obj, with
(apply f (meta obj) args) as its metadata.
> (defn a [blah] (with-meta blah {:type ::incredible}))
> (defn b [foo] (vary-meta (a foo) assoc ::b 2))
> ^(b []) ;; => {:user/b 2, :type :user/incredible}
-Phil
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