在 Scheme 中编写最小值过程的另一种方法? [英] Another way of writing a mimum value procedure in Scheme?

问题描述

因此，如果我有以下内容，它将返回一组四个数字中的最小值:

So if i have the following, which returns the smallest value out of a set of four numbers:

(define (minimum2 a b c d)
  (cond ((and (< a b) (< a c) (< a d)) a)
        ((and (< b c) (< b d)) b)
        ((< c d) c)
        (else d)))

但是，我想这样写，我比较 a 和 b 并找到两者之间的最小值，然后比较 c 和 d，并找到它们之间的最小值，然后将这两个最小值放在一起以找到实际最小值.如果我写的东西很难理解，可以把它想象成一个锦标赛括号，其中 a 玩" b，赢家玩 c 和 d 之间的另一个赢家.预先感谢您的帮助！

But, I want to write it so that I compare a to b and find the smallest value between those two, then compare c and d, and find the smallest value between those, and then compare those two smallest values together to find the actual minimum. If what I wrote was tough to understand, think of it like a tournament bracket, where a "plays" b, and the winner plays the other winner between c and d. Thank you in advance for the help!

推荐答案

这是一种方法:

(define (min4 a b c d)
  (define (min2 x y)
    (if (< x y) x y))
  (min2 (min2 a b) (min2 c d)))

另一种方法，如果您不想使用内部函数:

Another way to do it, if you don't want to use an internal function:

(define (min4 a b c d)
  (let ((min-ab (if (< a b) a b))
        (min-cd (if (< c d) c d)))
    (if (< min-ab min-cd) min-ab min-cd)))

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