proxy wierdness.clj

(ns user
  (:require [clojure.contrib [string :as s]]))

(defprotocol PDimension
  (dimensions [x]))

(defn unit [x dims]
    (proxy [java.lang.Number user.PDimension]
    []
      (byteValue [] (byte x))
      (doubleValue [] (double x))
      (floatValue [] (float x))
      (intValue [] (int x))
      (longValue [] (long x))
      (dimensions [] dims)
      (toString [] (str x " " (s/join " " (map (fn[[k v]] (str k " " v)) dims))))
      ))

(def area {:length 2})

(defn unit-mult
  [& args]
  (unit (apply * args) (apply merge-with + (map dimensions args))))

(defn unit-div
  [& args]
  (unit (apply / args) (apply merge-with - (map dimensions args))))

;;Everything is cool...
user=> (take 10 (iterate unit-div (unit 1 area))))
(1 :length 2
 1 :length 2
 1 :length 2
 1 :length 2
 1 :length 2
 1 :length 2
 1 :length 2
 1 :length 2
 1 :length 2
 1 :length 2)

;Huh?
user=> (take 10 (iterate unit-mult (unit 1 area)))
(1 :length 2
 1 :length 2 :length 2
 1 :length 2 :length 2 :length 2
 1 :length 2 :length 2 :length 2 :length 2
 1 :length 2 :length 2 :length 2 :length 2 :length 2
 1 :length 2 :length 2 :length 2 :length 2 :length 2 :length 2
 1 :length 2 :length 2 :length 2 :length 2 :length 2 :length 2 :length 2
 1 :length 2 :length 2 :length 2 :length 2 :length 2 :length 2 :length 2 :length 2
 1 :length 2 :length 2 :length 2 :length 2 :length 2 :length 2 :length 2 :length 2 :length 2
 1 :length 2 :length 2 :length 2 :length 2 :length 2 :length 2 :length 2 :length 2 :length 2 :length 2)

;Weirder
user=> (map dimensions (take 10 (iterate unit-mult (unit 1 area))))
({:length 2}
 {:length 2}
 {:length 2}
 {:length 2}
 {:length 2}
 {:length 2}
 {:length 2}
 {:length 2}
 {:length 2}
 {:length 2})