我有一个Clojure函数:
(defn f [arg1 arg2]
...)
我想测试
arg1
和arg2
是否为数字(只有数字类型可以通过-不是数字格式化的字符串)。当然,有很多方法可以做到这一点,但我想尽可能地达到惯用语的效果。有什么建议吗?编辑:我知道
:pre
。任何关于是否适当/必要处理此操作的评论将不胜感激。我有一个Clojure函数:
(defn f [arg1 arg2]
...)
arg1
和arg2
是否为数字(只有数字类型可以通过-不是数字格式化的字符串)。当然,有很多方法可以做到这一点,但我想尽可能地达到惯用语的效果。有什么建议吗?:pre
。任何关于是否适当/必要处理此操作的评论将不胜感激。预先条件可以做到这一点:
(defn test [arg1 arg2]
{:pre [(number? arg1) (number? arg2)]}
(+ arg1 arg2))
(test 1 2)
=> 3
(test 1 "2")
=> Assert failed: (number? arg2)
请查看http://clojure.org/special_forms#toc9了解更多信息。
你可能需要使用number?
函数。也许可以测试一下(and (number? arg1) (number? arg2))
。
不久前,Brian Carper建议使用宏和一系列函数来验证不同类型的数字参数:
;; Suggested by Brian Carper at:
;;https://dev59.com/9XI-5IYBdhLWcg3w3cc8
(defmacro assert* [val test]
`(let [result# ~test]
(when (not result#)
(throw (IllegalArgumentException.
(str "Test failed: " (quote ~test)
" for " (quote ~val) " = " ~val))))))
(defmulti validate* (fn [val test] test))
(defmethod validate* :prob [x _]
(assert* x (and (number? x) (pos? x) (<= x 1.0))))
(defmethod validate* :posint [x _]
(assert* x (and (integer? x) (pos? x))))
(defmethod validate* :non-negint [x _]
(assert* x (and (integer? x) (not (neg? x)))))
(defmethod validate* :posnum [x _]
(assert* x (and (number? x) (pos? x))))
(defmethod validate* :percentage [x _]
(assert* x (and (number? x) (pos? x) (<= x 100))))
(defmethod validate* :numseq [x _]
(assert* x (and (not (empty? x)) (seq? x) (every? number? x))))
(defmethod validate* :nonzero-numseq [x _]
(assert* x (and (not (empty? x)) (seq? x) (every? #(and (number? %) (not (zero? %))) x))))
(defmethod validate* :posint-seq [x _]
(assert* x (and (not (empty? x)) (seq? x) (every? #(and (integer? %) (pos? %)) x))))
(defmethod validate* :prob-seq [x _]
(assert* x (and (not (empty? x)) (seq? x) (every? #(and (number? %) (pos? %) (<= % 1.0)) x))))
(defmethod validate* :default [x _]
(throw (IllegalArgumentException.
(str "Unrecognized validation type"))))
(defn validate [& tests]
(doseq [test tests] (apply validate* test)))
(defn f [arg1 arg2]
"arg1 must be a positive integer, arg2 must be a positive number"
(validate [arg1 :posint] [arg2 :posnum])
...
)
:pre
呢?你觉得在这里不使用它是否可以? - charleslparker:pre
还不存在,而我已经习惯了使用宏。我认为使用宏可以减少打字量;例如,想象一下必须为:nonzero-numseq
键入条件。 :pre
可能更适合一次性、非常特定的条件,例如测试特定值而不是整个数字类别。 - clartaq我已经为这个目的发明了Dire!
(defn f [a b]
(+ a b))
(defprecondition f
:args-numeric
(fn [a b & more]
(and (number? a) (number? b))))
(defhandler f
{:precondition :args-numeric}
(fn [e & args] (apply str "Failure for argument list: " (vector args))))
(supervise f "illegal" "args")
我在搜索同样的东西时发现了this:
(defmacro verify-my-arg
"Like assert, except for the following differences:
1. does not check for *assert* flag
2. throws IllegalArgumentException"
[err-msg arg]
`(if ~arg true
(throw (IllegalArgumentException. ~err-msg))))
然后你可以像这样使用它:
(defn foo [m]
{:pre [(verify-my-arg "m must be a map" (map? m))]}
(println m))
希望这对你有所帮助!(所有功劳归功于谷歌小组中Shantanu Kumar的原始答案)
(defn add [^:number a ^:number b] (+ a b))
:pre
而使用其他东西,这会是不好的形式吗?我恰好处于一个有点困难的情况下(尽管我认为你的答案可能是大多数人想要的)。 - charleslparker:pre
很困难? - Justin Kramer