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

Official Documentation

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Arities
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   [& vars]

Docstring
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  Returns true if all of the vars provided as arguments have any bound value, root or thread-local.
   Implies that deref'ing the provided vars will succeed. Returns true if no vars are provided.

Source

(defn bound?
  "Returns true if all of the vars provided as arguments have any bound value, root or thread-local.
   Implies that deref'ing the provided vars will succeed. Returns true if no vars are provided."
  {:added "1.2"
   :static true}
  [& vars]
  (every? #(.isBound ^clojure.lang.Var %) vars))

Example 1

Edit
(def foobar)
;; => #'user/foobar

(bound? #'foobar)
;; => false

(def boing 10)
;; => #'user/boing

(bound? #'boing)
;; => true

(defn plus3 [n] (+ 3 n))
;; => #'user/plus3

(bound? #'plus3)
;; => true

Uses on crossclj