在Common Lisp中一起压缩列表-"and"问题 [英] Zipping lists together in Common Lisp - Problem with "and"

问题描述

我想做的是创建一个函数zip(现在要注意，这不是家庭作业)，该函数同时遍历多个列表，将一个函数应用于每个元素列表，如下所示:

What I am trying to do is create a function zip (note now that this is not homework) that iterates through multiple lists simultaneously, applying a function to each list of elements, like so:

(zip f '(1 2 3) '(4 5 6) '(7 8 9)) = (list (f 1 4 7) (f 2 5 8) (f 3 6 9))
(zip f '(1 2 3 4) '(5 6) '(7 8 9)) = (list (f 1 5 7) (f 2 6 8))

基本上，当任何列表用完元素时，它就会停止.这是我目前的尝试:

Basically, it stops when any list runs out of elements. Here is my current attempt:

(defun zip (f &rest lists)
  (if (apply and lists) ; <- Here is where I think the problem is.
    (cons (apply f (mapcar #'car lists)) (zip f &rest (mapcar #'cdr lists)))
    nil))

我想知道如何修复条件语句以与and一起使用，或达到某种效果.我认为问题出在and是宏.我还想知道是否已经有内置函数可以做到这一点.

I would like to know how fix the conditional statement to work with and, or something to that effect. I think the problem arises from and being a macro. I would also like to know if there is a built-in function for doing this already.

推荐答案

您正在重新实现mapcar

? (mapcar #'list '(1 2 3) '(4 5 6) '(7 8 9))
((1 4 7) (2 5 8) (3 6 9))
? (mapcar #'list '(1 2 3 4) '(5 6) '(7 8 9))
((1 5 7) (2 6 8))
? (mapcar #'+ '(1 2 3) '(4 5 6) '(7 8 9))
(12 15 18)
? (mapcar #'+ '(1 2 3 4) '(5 6) '(7 8 9))
(13 16)

顺便说一句，您想要在代码中代替all的函数是and

BTW, the function you want in your code in place of all is and

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