将 Clojure 宏视为函数 [英] Treat Clojure macro as a function

问题描述

如何使 Clojure 宏充当函数，以便我可以将其作为参数传递?我希望必须以某种方式包装它.

How can I cause a Clojure macro to act as a function, so I can pass it as an argument for example? I would expect to have to wrap it somehow.

我不希望包装版本的行为与原始宏完全相同(按名称调用与按值调用的差异)，但在这并不重要的少数情况下它会很有用.

I would not expect the wrapped version to behave exactly the same as the original macro (differences of call by name vs call by value), but it would be useful in a few cases where this wasn't important.

推荐答案

如果我没理解错的话，你可以把它包装在一个函数中.

If I'm understanding you correctly, you can just wrap it in a function.

将平方函数的这个(愚蠢的)实现视为宏:

Consider this (silly) implementation of a squaring function as a macro:

(defmacro square [x]
  (list * x x))

如您所知，直接将其作为 arg 传递是行不通的:

Passing it directly as an arg won't work, as you know:

user=> (map square [1 2 3 4 5])
java.lang.Exception: Can't take value of a macro: #'user/square (NO_SOURCE_FILE:8)

但是将它包装在一个函数中可以解决问题:

But wrapping it in a function will do the trick:

user=> (map #(square %) [1 2 3 4 5])
(1 4 9 16 25)

或者(更邪恶一点)，您可以制作另一个宏来进行更通用的包装:

Alternatively (and quite a bit more evil-ly), you could make another macro to do a more generic wrapping:

(defmacro make-fn [m] 
  `(fn [& args#] 
    (eval `(~'~m ~@args#))))

user=> (map (make-fn square) [1 2 3 4 5])
(1 4 9 16 25)

我会坚持使用正常的函数包装，并跳过最后一个 hack！:)

I'd stick with the normal function wrapping, and skip this last hack! :)

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