clojure - Wrong number of arguments for a simple function -

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can explain behavior in clojure code below? don't it. clojure somehow replace or "optimize" function arguments? why calling function single nil argument result in arityexception?

(defn foo [bar] (reduce #(%1) bar))  (foo nil) -> arityexception wrong number of args (0) passed to: test$foo$fn  clojure.lang.afn.throwarity (afn.java:437)

see (doc reduce):

[...] if coll contains no items, f must accept no arguments well, , reduce returns result of calling f no arguments. [...]

here coll nil, being treated collection containing no items (as in similar contexts), , f #(%1).

thus #(%1) being called no arguments , ends throwing exception see.


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