def-type-multis.clj

;; wouldn't it be nice if...

(def-type-multis DataRow
  (get-column-names [this])
  (get-value [this column-name]))

(defmethods DataRow
  clojure.lang.Associative
  (get-column-names [this]
    (range (count this)))
  (get-value [this column-name]
    (nth this column-name)))

;; so make it happen...

(defn type* [obj & _] (type obj))

(defmacro def-type-multis [name & methods]
  `(do
     ~@(for [[method-name] methods]
         `(defmulti ~method-name type*))))

(defmacro defmethods [name dispatch-value & methods]
  `(do
     ~@(for [[method-name & more] methods]
         `(defmethod ~method-name ~dispatch-value ~more))))