fancy-mod.clj

(defn fancy-mod
  "Takes the following parameters and
   returns a function which takes two integer numbers.

   - operator-fn => Mathematical Operator : + OR * OR / OR -
   - mod-by => number to mod by, example 2.
   - output-fn => str or int.

   Example:
   ((fancy-mod + 2 str) 10 11)
   ;;=> \"2\"

   Also can be used like
   > (def mod-by-3->int (fancy-mod + 3 int))
   > (mod-by-3->int 11 11)
   ;;=> 1

   Note: Throws exception if invalid parameters passed!"
  [operator-fn mod-by output-fn]
  {:pre [(#{+ - / *} operator-fn)
         (integer? mod-by)
         (#{str int} output-fn)]}
  (fn [num1 num2]
    {:pre [(integer? num1)
           (integer? num2)]}
    (output-fn (#(mod % mod-by)
                (operator-fn num1
                             num2)))))