如何在球拍中将列表作为参数列表传递? [英] How do I pass a list as a list of arguments in racket?

问题描述

我有一个这样的声明:

 ((lambda (a b c) (+ a b c)) 1 2 3) ; Gives 6

我想也可以将其传递给列表:

And I would like to be able to also pass it a list as so:

((lambda (a b c) (+ a b c)) (list 1 2 3))

...除外，因为所有列表都以"a"形式传递，因此无法正常工作.有没有一种方法可以将列表分解为参数?

...except this doesn't work because the entire list is passed as 'a.' Is there is a way to explode the list into arguments?

我正在寻找的东西类似于Python中的*字符.对于那些不熟悉语法的人:

What I'm looking for is something similar to the * character in Python. For those of you unfamiliar with the syntax:

 def sumthree(a, b, c):
   print a + b + c

 sumthree(1, 2, 3) # Prints 6
 sumthree(*(1, 2, 3)) # Also prints 6

推荐答案

该操作称为apply.

(apply + (list 1 2 3))   ; => 6

apply扩展"最后一个参数；以前的所有参数都按原样传递.这些都是一样的:

apply "expands" the last argument; any previous arguments are passed as is. So these are all the same:

(apply + 1 2 3 (list 4 5 6))
(apply + (list 1 2 3 4 5 6))
(+ 1 2 3 4 5 6)

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