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

Official Documentation

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Arities
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   [protocol atype]

Docstring
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  Returns true if atype extends protocol

Source

(defn extends? 
  "Returns true if atype extends protocol"
  {:added "1.2"}
  [protocol atype]
  (boolean (or (implements? protocol atype) 
               (get (:impls protocol) atype))))

Example 1

Edit
(defprotocol Area (get-area [this]))
;; => Area

(defrecord Rectangle [width height]
  Area
  (get-area [this]
    (* width height)))
;; => user.Rectangle

(extends? Area Rectangle)
;; => true

Uses on crossclj