Question

I’m trying to create a function to create a new basewith another struct as a base, and as a start I attempted to make a macro that would create a new struct with the same fields as the old one. The macro I have which i thought should do this is below, but it is giving the following error:

java.lang.Exception: Can't use qualified name as parameter: user/p1__132 

Macro:

(defmacro prototype [structure obj]
  `(apply struct ~structure (map #(~obj %) (keys ~obj))))

Example of use:

(defstruct bintree :data :left :right)
(def a (struct bintree 3))
(prototype bintree a)

The desired output in this case would be

{:data 3 :left nil :right nil}

Answer 1

The link seth posted as a comment to your question contains the answer (the culprit is the way arguments to anonymous functions are handled); the following, using a gensym argument, should work:

(defmacro prototype [structure obj]
  `(apply struct ~structure (map (fn [x#] (~obj x#)) (keys ~obj))))