modification of time (core) function to return the elapsed time in float, instead of formated string.

my-time

(defn my-time
  "This is a construction above core 'time' function to 
   return the time elapsed as a float, instead of a formated string.
   Usage example: (my-time + 2 1)"
  [f & args]
  (Float/parseFloat (first (re-find #"(\d+\.\d+)" (with-out-str (time (apply f args)))))))