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 <bra...@nordakademie.de> wrote:
> ... instead of an exception?
>
> Can anyone explain it to me?
>
> Johannes
>
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