while->

while-macro.clj

(defmacro while->
  "Takes a predicate, expression, and forms. Threads expr 
  through each form for which applying pred to the returned
  value is true. Threading short circuits after the first 
  false expression."
  [pred expr & forms]
  `(if (~pred ~expr)
     ~(if (not-empty forms)
        (let [next-expr `(-> ~expr ~(first forms))]
           `(if (~pred ~next-expr)
              (while-> ~pred ~next-expr ~@(rest forms))
              ~expr))
        expr)))

;; EXAMPLES

(while-> number? 3 (+ 2) (str " lemon") (+ 100)) ;=> 5

(while-> number? 3 (+ 2) inc (* 100)) ;=> 600

(while-> number? "Hello World!" first) ;=> nil

TODO:
1 ) Check first (~pred ~expr) only once, then use loop/recur on an inner loop
2 ) Remove double eval of next-expr (in if condition and in recursive while-> call)