utils.clj

(defn increment-keys
  "Given a map and a list of keys, this will return an identical map with those keys
   with those keys incremented.
    
   Keys with a null value will be set to 1."
  [src-map & xs]
  (into src-map (map #(vector %1 (inc (get src-map %1 0))) xs)))

; Example (increment-keys {:a 2} :a :b) => {:a 3 :b 1}