Clojure宏剖析

http://bryangilbert.com/blog/2013/07/30/anatomy-of-a-clojure-macro/

;; Before
(->>> 1       
  (+ _ 2)     
  (+ 3 _)     
  (- 50 _)    
  (/ _ 2))    

;; After (macroexpansion)
(let [init 1]
  (let [res0 (+ init 2)]
    (let [res1 (+ 3 res0)]
      (let [res2 (- 50 res1)]
        (let [res3 (/ res2 2)]
          res3)))))

  (defn convert-forms [val [next-form & other-forms]]               ; 1
    (if (nil? next-form)                                            ; 2
      val                                                           
      (let [next-val (gensym)]                                      ; 3
        `(let [~next-val ~(replace-underscores next-form val)]      ; 4
           ~(convert-forms next-val other-forms)))))                ; 5

(convert-forms 2 '((+ _ 1) (+ 4 _))) ; => 
    ; (clojure.core/let [G__1166 (+ 2 1)] 
    ;   (clojure.core/let [G__1167 (+ 4 G__1166)] 
    ;     G__1167))

1) 2=val, '((+ _ 1) (+ 4 _)) = [next-form & other-forms]
其中next-form=(+ _ 1), other-forms=(+ 4 _)

next-form != nil,