该方案等效于元组拆包? [英] What is scheme's equivalent of tuple unpacking?

问题描述

在Python中，我可以执行以下操作:

In Python, I can do something like this:

t = (1, 2)
a, b = t

...并且a将为1，b将为2.假设我在Scheme中有一个列表'(1 2).有什么办法可以与let做类似的事情吗?如果有什么不同，我正在使用球拍.

...and a will be 1 and b will be 2. Suppose I have a list '(1 2) in Scheme. Is there any way to do something similar with let? If it makes a difference, I'm using Racket.

推荐答案

在球拍中，您可以使用

In racket you can use match,

(define t (list 1 2))
(match [(list a b) (+ a b)])

以及和适用于列表，向量，结构等.对于多个值，您可以使用

That works for lists, vectors, structs, etc etc. For multiple values, you'd use define-values:

(define (t) (values 1 2))
(define-values (a b) (t))

或let-values.但是请注意，我不能将t定义为元组"，因为(大多数)方案实现中多个值不是一等值.

or let-values. But note that I can't define t as a "tuple" since multiple values are not first class values in (most) scheme implementations.

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