Overriding equals, hashCode and toString in a Clojure deftype
- by mikera
I'm trying to create a new type in Clojure using deftype to implement a two dimensional (x,y) coordinate, which implements a "Location" protocol.
I'd also like to have this implement the standard Java equals, hashCode and toString methods.
My initial attempt is:
(defprotocol Location
(get-x [p])
(get-y [p])
(add [p q]))
(deftype Point [#^Integer x #^Integer y]
Location
(get-x [p] x)
(get-y [p] y)
(add [p q]
(let [x2 (get-x q)
y2 (get-y q)]
(Point. (+ x x2) (+ y y2))))
Object
(toString [self] (str "(" x "," y ")"))
(hashCode [self] (unchecked-add x (Integer/rotateRight y 16)))
(equals [self b]
(and
(XXXinstanceofXXX Location b)
(= x (get-x b))
(= y (get-y b)))))
However the equals method still needs some way of working out if the b parameter implements the Location protocol.
What is the right approach? Am I on the right track?
