我应该使用函数还是宏来验证Clojure中的参数?

Clojure已经(未记录,可能会更改)支持 fn s

user> (defn divide [x y]
        {:pre [(not= y 0)]}
        (/ x y))
user> (divide 1 0)
Assert failed: (not= y 0)
   [Thrown class java.lang.Exception]

不过有点难看。

(defmacro assert* [val test]
  `(let [result# ~test]              ;; SO`s syntax-highlighting is terrible
     (when (not result#)
       (throw (Exception.
               (str "Test failed: " (quote ~test)
                    " for " (quote ~val) " = " ~val))))))

(defmulti validate* (fn [val test] test))

(defmethod validate* :non-zero [x _]
  (assert* x (not= x 0)))

(defmethod validate* :even [x _]
  (assert* x (even? x)))

(defn validate [& tests]
  (doseq [test tests] (apply validate* test)))

(defn divide [x y]
  (validate [y :non-zero] [x :even])
  (/ x y))

然后:

user> (divide 1 0)
; Evaluation aborted.
; Test failed: (not= x 0) for x = 0
;   [Thrown class java.lang.Exception]

user> (divide 5 1)
; Evaluation aborted.
; Test failed: (even? x) for x = 5
;   [Thrown class java.lang.Exception]

user> (divide 6 2)
3

我觉得这取决于验证的复杂性和数量,以及函数的性质。

如果您正在执行非常复杂的验证,那么应该将验证器从函数中分离出来。理由是你可以用简单的来构建更复杂的。

例如,你写:

2. 确认值大于零的验证器,
3. 使用1和2确保值是大于零的非空值列表。

如果您只是在做大量的简单验证,而问题是冗长(例如,您有50个函数都需要非零整数),那么宏可能更有意义。

一个你 如果您希望修改语言以自动将测试添加到块中定义的任何函数中,例如:

(with-function-validators [test1 test2 test4]  
    (defn fun1 [arg1 arg2] 
        (do-stuff))
    (defn fun2 [arg1 arg2] 
        (do-stuff))
    (defn fun3 [arg1 arg2] 
        (do-stuff)))