Because ' is a reader macro which expands to the list (quote some-symbol),
so the metadata is applied to the list, and not the symbol. You can verify
this in the REPL - (meta (quote ^:abc 'some-symbol))
On Tuesday, May 5, 2015 at 5:43:19 PM UTC-4, Andy- wrote:
>
> Frankly, I would've (meta ^:abc 'some-symbol) expected to work. Maybe
> somebody else can weigh in on why this one is a no-go.
>
> On Tuesday, May 5, 2015 at 5:01:19 PM UTC-4, Andrey Antukh wrote:
>>
>> Thanks to both for the responses, but I stil not clearly understand.
>>
>> The documentation says very clearly that:
>>
>> In addition to with-meta, there are a number of reader macros (The
>> Reader: Macro Characters) for applying metadata to the expression following
>> it:
>> ^{:doc "How obj works!"} obj - Sets the metadata of obj to the provided
>> map.
>> Equivalent to (with-meta obj {:doc "How obj works!"})
>>
>>
>> (def foo ^:abc [1 2 3]) -> (meta foo) -> {:abc true}
>> (def foo ^:abc some-func) -> (meta foo) -> nil
>> (def foo ^:abc 'some-symbol) -> (meta foo) -> nil (In clojure
>> programming book uses example attaching metadata using the reader to the
>> symbol, but seems it not works as expected)
>>
>> Is a little bit confusing. The metadata documentation says clearly that
>> are equivalent, but are not equivalent.
>>
>>
>> Thank you very much again.
>>
>> Regards.
>> Andrey
>>
>> 2015-05-05 21:49 GMT+02:00 Andy- <[email protected]>:
>>
>>> In addition to James comment: IMO clojure.org/metadata should be
>>> clearer about this. It's mentioned more clearly on the reader page:
>>> http://clojure.org/reader#The%20Reader--Macro%20characters
>>> "The metadata reader macro first reads the metadata and attaches it to
>>> the next form read (see with-meta
>>> <http://clojure.github.io/clojure/clojure.core-api.html#clojure.core/with-meta>
>>> to
>>> attach meta to an object):"
>>>
>>> Stress on *next form read*.
>>>
>>> On Tuesday, May 5, 2015 at 2:31:40 PM UTC-4, Andrey Antukh wrote:
>>>>
>>>> Hi!
>>>>
>>>> I have some trouble with clojure metadata / reader and I do not know if
>>>> I'm doing something wrong.
>>>>
>>>> I have this code:
>>>>
>>>> (defn some-func [])
>>>>
>>>> (def func ^:abc some-func)
>>>>
>>>> (assert (= (meta func) {:abc true}))
>>>>
>>>> (def data [[:bar (with-meta some-func {:abc true})]
>>>> [:baz ^:abc some-func]])
>>>>
>>>> (assert (= (meta (get-in data [0 1])) {:abc true}))
>>>> (assert (= (meta (get-in data [1 1])) {:abc true}))
>>>>
>>>> It fails in the first assert and in the last (if I comment the first
>>>> one obviously). I do not understand why that form of metadata does not
>>>> works
>>>> as I expect (http://clojure.org/metadata)
>>>>
>>>> Thank you very much.
>>>>
>>>> Regards.
>>>> Andrey
>>>>
>>>> --
>>>> Andrey Antukh - Андрей Антух - <[email protected]> / <
>>>> [email protected]>
>>>> http://www.niwi.be <http://www.niwi.be/page/about/>
>>>> https://github.com/niwibe
>>>>
>>>
>>
>>
>> --
>> Andrey Antukh - Андрей Антух - <[email protected]> / <[email protected]
>> >
>> http://www.niwi.be <http://www.niwi.be/page/about/>
>> https://github.com/niwibe
>>
>
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