Get list of fields in struct

How would I find what fields a struct has? For example, if i have the following: ``` (defstruct bintree :data :left :right) (def a (struct bintree 0 nil nil)) ``` how would i get a list,set, or vector of (:data :left :right) from a? I've tried ``` (show a) ``` but this gives no methods that look correct.