Clojure: how to send remaining arguments "& args" into list?

Question

Is there any (reasonable) way to write this macro as a function?

(defmacro assocTop
          [v & args]
          `(push (pop ~v)
                 (assoc (peek ~v) ~@args)))

Given a vector of maps and some associations, the macro code applies the associations to the top/peeked map.

However, when trying to write it as a function, I can't figure out how to expand the ~@args in a legitimate way. In normal functions, is there a way to turn args, which I believe has the form (:a 3 :bb 44 :cd 90,...) into :a 3 :bb 44 :cd 90,... ,i.e. without the parens?

Jan · Accepted Answer · 2012-10-20 08:43:33Z

5

I guess you should use apply which will apply assoc to (peek v) and expanded args.

(defn assocTop
  [v & args]
  (push (pop v)
        (apply assoc (peek v) args)))
(=
  (assocTop [{:a :b} {:c :d} {:e :f, :g :h}] :e :z)
  [{:a :b} {:c :d} {:g :h, :e :z}]) ; => true

answered Oct 20, 2012 at 8:43

Jan

11.7k41 silver badges47 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

spacingissue Over a year ago

How come reduce doesn't work here but works with, say, (defn push [v & args] (reduce conj v args))?

Jan Over a year ago

@spacingissue, I don't see how do you want to use reduce in this case. Can you elaborate?

spacingissue Over a year ago

I guess I was thinking that applying assoc repeatedly on the answer would be the same as reduce. Is there a distinction to the push case (where you apply conj repeatedly on the answer)?

Collectives™ on Stack Overflow

Clojure: how to send remaining arguments "& args" into list?

1 Answer 1

3 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

3 Comments

Your Answer

Sign up or log in

Post as a guest

Related