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57

answers:

1

I'm working on a multimethod that needs to update a hash for a bunch of different things in a sequence. Looked fairly straitforward until I tried to enter the 'type of an array of X'.

(defmulti update-hash #(class %2))

(type (byte 1))
=> java.lang.Byte
(defmethod update-hash java.lang.Byte [md byte]
  (. md update byte))

(type (into-array  [ (byte 1)]))
=> [Ljava.lang.Byte;
(defmethod update-hash < WHAT GOES HERE > [md byte]
+2  A: 

Either of these should work:

(defmethod update-hash (Class/forName "[Ljava.lang.Byte;") [md byte] ...)

(defmethod update-hash (class (make-array Byte 0)) [md byte] ... )
Brian Carper
where does the name "[Ljava.lang.Byte;" come from?
Arthur Ulfeldt
It's some name the JVM uses internally to refer to arrays. You'll see it in plain Java sometimes too.
Brian Carper