对 Scheme 中 let 和 let* 之间的区别感到困惑 [英] Confused by the difference between let and let* in Scheme

问题描述

谁能简单解释一下区别?我不认为我从我咨询过的教科书/网站中理解了这个概念.

Can anyone explain the difference simply? I don't think I understand the concept from the textbooks/sites I have consulted.

推荐答案

如果使用 let，则不能引用出现在同一 other 绑定>let 表达式.

If you use let, you can't reference other bindings which appear in the same let expression.

例如，这行不通:

(let ((x 10)
      (y (+ x 6))) ; error! unbound identifier: x
  y)

但是如果你使用 let*，就可能引用出现在同一个 let* 表达式中的 previous 绑定:

But if you use let*, it is possible to refer to previous bindings which appear in the same let* expression:

(let* ((x 10)
       (y (+ x 6))) ; works fine
  y)
=> 16

此处都在文档中.

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