gistfile1.clj

(defn fmap
  "Filtering map. Like map, but removes nils from the result seq."
  [& args]
  (filter identity (apply map args)))

(defn update-matching
  "Updates the given object(s) with fns selected by predicates.

  (update-matching object(s) predicate-fn*)

  predicate-fn => predicate update-fn

If the predicates of several update fns match, they are called in the
  order in which they were given."
  [object & predicate-fns]
  (let [update-fns (fmap (fn [[predicate update-fn]]
                           (when (predicate object)
                             update-fn))
                         (partition 2 predicate-fns))]
    ((apply comp (reverse update-fns)) object)))