jneen · November 22, 2014 20:55 · clojj · Feb 17, 2015
diff --git a/variant-multimethods.clj b/variant-multimethods.clj
 ; it's a bit cumbersome to set up and there's the unfortunate need to ignore the tag
 ; in the individual methods, but this allows you to leave the interpretation of open 
 ; variants, well, *open* for extension by multimethod.

 ; dispatch off the first argument, which will be the tag
 (defmethod command-multi (fn [tag & data] tag))

 ; the first argument to the *method* is still the tag
 (defmulti command-multi :print [_ val] (println val))
 (defmulti command-multi :read [_ fname] (slurp fname))

 ; partially applying `apply` so that the variant vectors
 ; get flattened - it's a bit odd but gets the job done
 (def command (partial apply command-multi))

 (command [:print "hello world"]) ; prints "hello world"
 (command [:read "./project.clj"]) ; returns the contents of project.clj
	; it's a bit cumbersome to set up and there's the unfortunate need to ignore the tag
	; in the individual methods, but this allows you to leave the interpretation of open
	; variants, well, open for extension by multimethod.

	; dispatch off the first argument, which will be the tag
	(defmethod command-multi (fn [tag & data] tag))

	; the first argument to the method is still the tag
	(defmulti command-multi :print [_ val] (println val))
	(defmulti command-multi :read [_ fname] (slurp fname))

	; partially applying `apply` so that the variant vectors
	; get flattened - it's a bit odd but gets the job done
	(def command (partial apply command-multi))

	(command [:print "hello world"]) ; prints "hello world"
	(command [:read "./project.clj"]) ; returns the contents of project.clj