如何在Ruby中获取随机数(How to get a random number in Ruby)

如何在Ruby中获取随机数(How to get a random number in Ruby)

如何在0和n之间生成随机数？

How do I generate a random number between 0 and n?

最满意答案

rand(range)什么问题？

从Ruby随机数 ：

如果您需要一个随机整数来模拟一面六面的模具，您可以使用： 1 + rand(6) 。 可以用2 + rand(6) + rand(6)模拟掷骰子。

最后，如果你只需要一个随机的浮点数，只需调用rand没有参数。

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正如Marc-AndréLafortune在下面的回答中所提到的那样， Ruby 1.9.2具有自己的Random类 （Marc-André自己帮助调试 ，因此该功能的1.9.2目标 ）。

例如，在你需要猜测10个数字的游戏中 ，您可以使用以下方式初始化它们：

10.times.map{ 20 + Random.rand(11) } #=> [26, 26, 22, 20, 30, 26, 23, 23, 25, 22]

注意：

马克 - 安德烈·拉福顿 （ Marc-AndréLafortune ）再次详细解释（使用Random.new ）通常使用Random.new.rand(20..30) （使用Random.new ）并不是个好主意。

但是如果不使用Random.new ，那么类方法rand只会在注释中指出一个max ，而不是一个Range ，而不是一个Range 。 只有实例方法可以采用Range ，如通过生成一个7位数的随机数来说明的。

这就是为什么Random.new.rand(20..30)的等价物将是20 + Random.rand(11) ，因为Random.rand(int)返回“大于或等于零并小于参数 “ 20..30包括30，我需要提出一个0到11之间的随机数，不包括11。

Use rand(range)

From Ruby Random Numbers:

If you needed a random integer to simulate a roll of a six-sided die, you'd use: 1 + rand(6). A roll in craps could be simulated with 2 + rand(6) + rand(6).

Finally, if you just need a random float, just call rand with no arguments.

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As Marc-André Lafortune mentions in his answer below (go upvote it), Ruby 1.9.2 has its own Random class (that Marc-André himself helped to debug, hence the 1.9.2 target for that feature).

For instance, in this game where you need to guess 10 numbers, you can initialize them with:

10.times.map{ 20 + Random.rand(11) } #=> [26, 26, 22, 20, 30, 26, 23, 23, 25, 22]

Note:

Using Random.new.rand(20..30) (using Random.new) generally would not be a good idea, as explained in detail (again) by Marc-André Lafortune, in his answer (again).

But if you don't use Random.new, then the class method rand only takes a max value, not a Range, as banister (energetically) points out in the comment (and as documented in the docs for Random). Only the instance method can take a Range, as illustrated by generate a random number with 7 digits.

This is why the equivalent of Random.new.rand(20..30) would be 20 + Random.rand(11), since Random.rand(int) returns “a random integer greater than or equal to zero and less than the argument.” 20..30 includes 30, I need to come up with a random number between 0 and 11, excluding 11.