jneen/variant-multimethods.clj

## 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