Example of extending native Java array types to Clojure protocols

extend-array-type.clj

;   Copyright (c) Daniel Kwiecinski. All rights reserved.
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; Example of extending native Java array types to Clojure protocols

(defn array-of [t]
  (.getClass (java.lang.reflect.Array/newInstance t 0)))


(defprotocol P
  (ppp [it]))


(extend-type Object
  P
  (ppp [s]
    (format "<%s>" s)))


(extend-type String
  P
  (ppp [s]
    (format "\"%s\"" s)))

(extend-type (array-of Object)
  P
  (ppp [a]
    (apply str
      (flatten
        ["Array["
         (interpose ", "
           (map
             #(ppp %)
             a))
         "]"]))))
  

; => (ppp (to-array [1 2 3 4]))
; "Array[<1>, <2>, <3>, <4>]"
; => (ppp (to-array ["foo" "bar"]))
; "Array[\"foo\", \"bar\"]"