Thank you for the explanation; until now I associated this behavior only to
keywords not not symbols.
Johannes
Am Samstag, 26. Oktober 2019 19:12:11 UTC+2 schrieb Andy Fingerhut:
>
> Both symbols and keywords, when placed inside of an expression in the
> first position, e.g. (:my-keyword my-map), or ('some-symbol my-map), behave
> as functions that "look themselves up" in the map that is the first
> argument, and if that symbol or keyword is a key in that map, the
> associated value is returned from the expression. This is most often used
> for keywords, but it does also work for symbols, which is what is happening
> in your expression. The number `1` is not a map, and both this kind of
> lookup expression, as well as the function `get`, have always returned nil
> when the thing-to-be-looked-up-in is not a map or set (or anything else
> that implements the appropriate lookup interface methods being used in the
> Java implementation under the covers there).
>
> Some other examples of similar behavior:
>
> $ clj
> Clojure 1.10.1
> user=> ('f 1)
> nil
> user=> ('f 1 :not-found)
> :not-found
> user=> ('f {'f 17 :bar 8})
> 17
> user=> ('f {:bar 8} :not-found-value)
> :not-found-value
> user=> (get {'f 17 :bar 8} 'f)
> 17
> user=> (get 1 'f)
> nil
> user=> (get 1 'f :not-found)
> :not-found
>
> Andy
>
>
>
> On Sat, Oct 26, 2019 at 10:05 AM Johannes <[email protected]
> <javascript:>> wrote:
>
>> ... instead of an exception?
>>
>> Can anyone explain it to me?
>>
>> Johannes
>>
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>
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