将函数映射到elisp中的两个列表 [英] Mapping a function over two lists in elisp

问题描述

在常见的Lisp中，我可以这样做:

In common lisp I can do this:

(mapcar #'cons '(1 2 3) '(a b c))

=> ((1 . A) (2 . B) (3 . C))

我如何在elisp中做同样的事情?当我尝试时，出现错误:

How do I do the same thing in elisp? When I try, I get an error:

(wrong-number-of-arguments mapcar 3)

如果elisp的mapcar一次只能处理一个列表，那么将两个列表组合成一个列表的理想方式是什么?

If elisp's mapcar can only work on one list at a time, what is the idomatic way to combine two lists into an alist?

推荐答案

您想要mapcar*，它接受一个或多个序列(不只是Common Lisp中的列表)，而且对于一个序列参数，其作用与常规mapcar.

You want mapcar*, which accepts one or more sequences (not just lists as in Common Lisp), and for one sequence argument works just like the regular mapcar.

(mapcar* #'cons '(1 2 3) '(a b c))
((1 . A) (2 . B) (3 . C))

即使未定义，您也可以轻松地自己滚动:

And even if it weren’t defined, you could easily roll your own:

(defun mapcar* (f &rest xs)
  "MAPCAR for multiple sequences"
  (if (not (memq nil xs))
    (cons (apply f (mapcar 'car xs))
      (apply 'mapcar* f (mapcar 'cdr xs)))))

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