小编M. *_*ong的帖子

我正在关注clojure.spec的指南(http://clojure.org/guides/spec).我被之间的区别感到困惑alt,并or进行序列规范.

对我来说,以下两个例子同样有效.那两者之间的区别是什么？

; Use `alt`
(s/def ::config (s/* (s/cat :prop string?
                        :val (s/alt :s string? :b boolean?))))
(s/explain ::config ["-server" "foo" "-verbose" true "-user" 13])

; Use `or`
(s/def ::config (s/* (s/cat :prop string?
                        :val (s/or :s string? :b boolean?))))
(s/explain ::config ["-server" "foo" "-verbose" true "-user" 13])

(class (range 10))
;=> clojure.lang.LazySeq

(class (seq (range 10))
;=> clojure.lang.ChunkedCons

据我了解，LazySeq已经是一个序列，因为：

(seq? (range 10))
;=> true

我的谜题是以下示例:

(defmacro macro1 [x]
  (println x))

(defn func1 [x]
  (println x))

(defmacro macro2 [x]
  `(macro1 ~x)
  (func1 x))

(defmacro macro3 [x]
  (func1 x)
  `(macro1 ~x))

(println "macro2")
(macro2 hello)

(println "macro3")
(macro3 hello)

令人惊讶的是,输出是:

macro2
hello
macro3
hello
hello

为什么macro2和macro3的输出不同？根据我的理解,宏内部宏的所有调用都可以用函数代替(除了重用的原因).我的理解有什么不对吗？

谢谢迈克尔的澄清.我的一般问题是如何在宏内部使用函数或宏来操作s-expression.我想知道它们是否可以交换使用,除了它们在不同的阶段被唤醒.另一个例子:

(defn manipulate-func [x]
  (list + x 1))

(defmacro manipulate-macro [x]
  (list + x 1))

(defmacro macro1 [x y]
  [(manipulate-func x) `(manipulate-macro ~y)])

(println (clojure.walk/macroexpand-all '(macro1 (+ 1 2) (+ 3 4))))
;; [(#<core$_PLUS_ clojure.core$_PLUS_@332b9f79> (+ 1 2) 1) (#<core$_PLUS_ …

为什么不进行类型检查extractEither？

data MyEither a b = MyLeft a | MyRight b
                    deriving (Read, Show)

extractEither :: MyEither a b -> c
extractEither (MyLeft p) = p

编译器显示:

Couldn't match type `a' with `c'
  `a' is a rigid type variable bound by
      the type signature for extractEither :: MyEither a b -> c
      at /Users/tongmuchenxuan/playground/test.hs:5:1
  `c' is a rigid type variable bound by
      the type signature for extractEither :: MyEither a b -> c
      at /Users/tongmuchenxuan/playground/test.hs:5:1
In the expression: …