domap.clj

(defn domap
  "A map for side-effects.  The argument order is the same as map, but
unlike map the function results are not retained.  Takes a function 
followed by any number of collections and applies the function to the 
first item in each coll, then the second etc.  Returns nil."
  [fn & colls]
  (let [num-colls (count colls)] 
    (doseq [args (partition num-colls (apply interleave colls))] 
      (apply fn args))))