是否可以将宏扩展为多个元素? [英] Is it possible to expand a macro into several elements?

问题描述

我想要一个宏my-macro，它可以扩展为1 2 3而不是(1 2 3)，这样

I want a macro my-macro which can expand to 1 2 3 rather than (1 2 3), so that

(list (my-macro) 4 5) -> (1 2 3 4 5)

这可能吗?

推荐答案

否，宏不能扩展为多个值.当您需要将宏扩展为多段代码时，通常要做的就是将返回值包装在progn中.

No, macros cannot expand to more than one value. The typical thing to do when you need a macro to expand to multiple pieces of code is to wrap the return value in a progn.

在注释的示例中，看起来好像您不是将宏用作语法抽象，而是将其作为廉价而愉悦的函数优化来使用，通常的响应是请不要这样做，这是错误的"并没有真正做到你想要的".

In your example in the comments, it looks as if you are using macros not as syntactic abstractions, but as cheap-and-cheerful function optimizations, the usual response to that is "please don't do it, it is wrong and doesn't actually do what you want".

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