multimethod groups

multimethod-groups.clj

(defmacro defmulti-group
  "Define a group of related multimethods."
  [& forms] `(do ~@(map #(cons 'defmulti %) forms)))

(defmacro defmethod-group
  "Implement a group of related multimethods sharing common dispatch values."
  [& specs]
  (letfn [(parse-impls [specs]
            (lazy-seq
             (when (seq specs)
               (let [dval (first specs),
                     [fns specs] (split-with list? (rest specs))]
                 (cons (cons dval fns) (parse-impls specs))))))]
    `(do ~@(mapcat (fn [[dval & fns]]
                     (map #(list* 'defmethod (first %) dval (rest %)) fns))
                   (parse-impls specs)))))