有没有更紧凑的方法来检查一个数字是否在一个范围内? [英] Is there a more compact way of checking if a number is within a range?

问题描述

我希望能够测试一个值是否在一个数字范围内.这是我当前的代码:

I want to be able to test whether a value is within a number range. This is my current code:

if ((year < 2099) && (year > 1990)){
    return 'good stuff';
}

有没有更简单的方法来做到这一点?例如，有没有这样的东西?

Is there a simpler way to do this? For example, is there something like this?

if (1990 < year < 2099){
    return 'good stuff';
}

推荐答案

在许多语言中，第二种方式会根据你想要的从左到右错误地评估.

In many languages, the second way will be evaluated from left to right incorrectly with regard to what you want.

例如，在 C 中，1990 <year 将评估为 0 或 1，然后变为 1 <2099，当然，这总是正确的.

In C, for instance, 1990 < year will evaluate to 0 or 1, which then becomes 1 < 2099, which is always true, of course.

Javascript 与 C 非常相似:1990 <year 返回 true 或 false，这些布尔表达式在数值上似乎分别等于 0 和 1.

Javascript is a quite similar to C: 1990 < year returns true or false, and those boolean expressions seem to numerically compare equal to 0 and 1 respectively.

但是在 C# 中，它甚至不会编译，给你错误:

But in C#, it won't even compile, giving you the error:

错误 CS0019: 运算符 '<'不能应用于bool"和int"类型的操作数

error CS0019: Operator '<' cannot be applied to operands of type 'bool' and 'int'

你从 Ruby 得到一个类似的错误，而 Haskell 告诉你不能在同一个中缀表达式中使用 < 两次.

You get a similar error from Ruby, while Haskell tells you that you cannot use < twice in the same infix expression.

在我的脑海中，Python 是我确定以这种方式处理中间"设置的唯一语言:

Off the top of my head, Python is the only language that I'm sure handles the "between" setup that way:

>>> year = 5
>>> 1990 < year < 2099
False
>>> year = 2000
>>> 1990 < year < 2099
True

最重要的是，第一种方式 (x < y && y < z) 始终是您最安全的选择.

The bottom line is that the first way (x < y && y < z) is always your safest bet.

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