Clojure macro for creating ratio converter functions.

defratios

(defmacro defratios
  "Defines two converter functions with num-expr being how many of a make up b.
For example, there are 100 centimeters in a meter.  To tell the program to make
 (centimeter->meter) and (meter->centimeter), use (defratios meter centimeters 100)"
  [a-symb b-symb num-expr]
  (and (= (type a-symb) clojure.lang.Symbol) (= (type b-symb) clojure.lang.Symbol)
   (let [ab-symb (symbol (arr a-symb b-symb))
        ba-symb (symbol (arr b-symb a-symb))]
    `(let [num# ~num-expr]
       (defn ~ab-symb [a#] (* a# num#))
       (defn ~ba-symb [b#] (/ b# num#))))))