方案 - 生成随机 [英] Scheme - generate random

问题描述

如何在 Scheme 中生成随机数?是否有特殊表格或我必须创建一个程序?如果是这样，我该怎么做?(我正在尝试创建一个名为 random-choice 的过程，该过程输入两种策略并随机返回一种.)

How do I generate random in Scheme? Is there a special form or would I have to create a procedure? And if so, how do I do that? (I'm trying to create a procedure called random-choice that inputs two strategies and returns one at random.)

推荐答案

该过程被调用，令人惊讶的是，random - 尽管确切的语法可能因使用的 Scheme 解释器而异(阅读文档！)，但总体思路如下:

The procedure is called, surprisingly enough, random - although the exact syntax might be different depending on the Scheme interpreter in use (read the documentation!), but the general idea is as follows:

(random)
=> 0.9113789707345018

为了返回两个可能的值之一，这将在 Racket 中起作用:

For returning one of two possible values, this will do the trick in Racket:

(define (random-choice a b)
  (if (zero? (random 2)) a b))

请注意，传递给 random 的 2 参数强制它随机返回两个可能值之一:0 或 1.因此，如果 (random 2) 计算结果为 0，则返回 a，否则返回 b.

Notice that the 2 argument passed to random forces it to randomly return one of two possible values: 0 or 1. So if (random 2) evaluates to 0 then a is returned, otherwise b is returned.

(random-choice 4 2)
=> 4
(random-choice 4 2)
=> 2

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