我如何在 Common Lisp 中重新实现反引号？

发布于 2024-10-09 23:09:43 字数 285 浏览 1 评论 0原文

我必须重新制作反引号（使用取消引用和取消引用拼接）而不使用内置读取器宏 `,@ 预期的行为是：

> (BACKQUOTE (A B (LIST ‘C ‘D) (COMA (LIST ‘E ‘F)
                               (COMA-AT (LIST ‘G ‘H)))
(A B (LIST ‘C ‘D) (E F) G H)

我尝试使用宏来执行此操作，但结果不是预期的。

非常感谢！！！

有什么可以做的提示吗？

原文

I have to remake backquote (with unquote and unquote-splicing) without using the builtins reader macros `,@
The behaviour expected is:

> (BACKQUOTE (A B (LIST ‘C ‘D) (COMA (LIST ‘E ‘F)
                               (COMA-AT (LIST ‘G ‘H)))
(A B (LIST ‘C ‘D) (E F) G H)

I try to do it with a macro but the results are no the expected.

Many thanks!!!

Any hints of what could be done?

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做个ˇ局外人 2024-10-16 23:09:43

http://lib.store.yahoo.net/lib/paulgraham/glsbq.lisp 有一个例子

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最终幸福 2024-10-16 23:09:43

对于那些在尝试理解保罗·格雷厄姆代码时接受简单且不正确的解决方案但它有效的人：

(defmacro backquote (expr)
  (labels
      ((step (p n)
             (append p
                     (if (atom n) (list n)
                       (case (car n)
                         ('comma (list (eval (cadr n))))
                         ('comma-at (eval (cadr n))))))))
    (list 'quote (reduce #'step (cons () expr)))))

欢迎更正和改进它的建议！

For Those Who well settle for a simple and incorrect solution but it works, while trying to understand the paul graham code:

(defmacro backquote (expr)
  (labels
      ((step (p n)
             (append p
                     (if (atom n) (list n)
                       (case (car n)
                         ('comma (list (eval (cadr n))))
                         ('comma-at (eval (cadr n))))))))
    (list 'quote (reduce #'step (cons () expr)))))

corrections and suggestions to improve it are welcome!

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