对出租计划与出租计划的分别感到困惑

Question

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

转载于:https://stackoverflow.com/questions/15003518/confused-by-the-difference-between-let-and-let-in-scheme

Answer 1

If you use let, you can't reference bindings previously defined in the same let expression. For example, this won't work:

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

But if you use let*, it's possible to refer to previous bindings in the same let* expression:

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

It's all here in the documentation.