如何在Common Lisp中的宏外部拼接到列表? [英] How do I splice into a list outside of a macro in Common Lisp?
问题描述
说我有一个函数foo:
Say I have a function foo:
(defun foo(xy& rest args)
...)
然后我想用功能栏将其包装:
And I later want to wrap it with a function bar:
(defun bar(x& rest args)
(foo x 100 args))
假设条形为然后这样称呼:(bar 50 1 2 3)
Assume bar was then called like this: (bar 50 1 2 3)
通过此设置,args是包含尾随参数的bar主体,因此当我将其传递给foo时,而不是得到(foo 50 100 1 2 3)
的值,我当然得到了(foo 50100'(1 2 3))
。如果这些是宏,我会在bar主体中使用``(foo,x 100,@ args)`将args拼接到函数调用中。 ,@@仅在反引号引起的列表中起作用。
With this setup, args is a list within the body of bar that holds the trailing parameters, so when I pass it to foo, instead of getting the equivalent of (foo 50 100 1 2 3)
I of course get (foo 50 100 '(1 2 3))
. If these were macros, I would use ``(foo ,x 100 ,@args)` within the body of bar to splice args into the function call. ,@ only works inside a backtick-quoted list, however.
我如何在常规函数中进行这种拼接?
How can I do this same sort of splicing within a regular function?
推荐答案
APPLY将调用其第一个参数及其后续参数,而最后一个参数必须是列表。因此:
APPLY will call its first argument with its subsequent arguments, and the last argument must be a list. So:
(apply #'foo x 100 args)
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