cond-as-> macro definition

cond-as->.clj

(defmacro cond-as->
  [value sym & clauses]
  (when (odd? (count clauses))
    (throw (IllegalArgumentException. "cond-as-> requires an even number of clauses")))

  (let [steps (partition 2 clauses)]
    (loop [val value, steps steps]
      (if (empty? steps)
        val
        (let [[test expr] (first steps)
              next-val `(let [~sym ~val]
                          (if ~test ~expr ~sym))]
          (recur next-val (rest steps)))))))

;; (cond-as-> 1 x true (+ x x) false (* x 2) true (- x 3))
;; => -1