if-thread.clj

(defmacro if->
  [exp t f]
  `(let [exp-val#          ~exp         
         [fn-t#  rest-t#]  ~(if (seq? t)
                              [(first t) (vec (next t))]
                              [t []])
         
         [fn-f#  rest-f#]  ~(if (seq? f)
                              [(first f) (vec (next f))]
                              [f []])]
     
     (if exp-val#
       (apply fn-t# (cons exp-val# rest-t#))
       (apply fn-f# (cons exp-val# rest-f#)))))

(if-> nil
      (+ 10)
      (println "is false"))

;; "nil is false"

(if-> 5
      (+ 10)
      (println "is false"))

;; => 15

(if-> 5
      inc
      (println "is false"))

;; => 6

(if-> (+ 2 3)
      inc
      (println "is false"))

;; => 6