Is it possible to overload Clojure multi-methods on arity?

Question

I have some code that uses multi-methods and would ideally like to overload the function (in this case, multi-function) so that I can pass in a higher order function to help wit

Answer 1

You can do that using multimethods as shown below example:

(defmulti which-colour-mm (fn [m & args] [(count args) (:colour m)]))
(defmethod which-colour-mm [0 :blue] [m] (print m))
(defmethod which-colour-mm [1 :blue] [m f] (f m))


user=> (which-colour-mm {:colour :blue :object :ball})
{:colour :blue, :object :ball}nil
user=> (which-colour-mm {:colour :blue :object :ball} print)
{:colour :blue, :object :ball}nil