functions as map keys

gistfile1.clj

(def testsToConst {
  (fn list?) :list,
  (fn vector?) :vector
;; etc...
})
;; filter keys in the map by evaluating them for a given col argument, 
;; take the first result, use that to get the entry from the map. 
(get testsToConst (first (filter (fn [fun] fun col) (keys testsToConst))))
;; this doesn't work reliably as vectors would be a special case and 
;; I don't yet know how to escape that when applying. Whatever.