store/[org.clojure/clojure "1.8.0"] clj::clojure.core/ifn?

Official Documentation

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Docstring
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  Returns true if x implements IFn. Note that many data structures
  (e.g. sets and maps) implement IFn

Source

(defn ifn?
  "Returns true if x implements IFn. Note that many data structures
  (e.g. sets and maps) implement IFn"
  {:added "1.0"
   :static true}
  [x] (instance? clojure.lang.IFn x))

Example 1

Edit
;; An anonymous function is a function as you'd expect
(ifn? #("my anonymous function"))
;; => true

;; Is a vector a function?
(ifn? [1 2 3])
;; => true

;; Sure is, lets call it.
([1 2 3] 0)
;; => 1

;; Maps and sets are functions, too.

;; a number is definitely not a function
(ifn? 1)
;; => false

;; but a symbol is
(ifn? 'foo)
;; => true

;; and so is a keyword
(ifn? :foo)
;; => true

Uses on crossclj