如何优雅地检查一个数字是否在一个范围内? [英] How to elegantly check if a number is within a range?

问题描述

如何使用 C# 优雅地做到这一点?

How can I do this elegantly with C#?

例如，一个数字可以介于 1 和 100 之间.

For example, a number can be between 1 and 100.

我知道一个简单的 if (x >= 1 && x <= 100) 就足够了；但是随着大量语法糖和不断添加到 C#/.Net 中的新功能，这个问题是关于更惯用(一个可以是优雅)的编写方式.

I know a simple if (x >= 1 && x <= 100) would suffice; but with a lot of syntax sugar and new features constantly added to C#/.Net this question is about more idiomatic (one can all it elegance) ways to write that.

性能不是问题，但请在不是 O(1) 的解决方案中添加性能说明，因为人们可能会复制粘贴建议.

Performance is not a concern, but please add performance note to solutions that are not O(1) as people may copy-paste the suggestions.

推荐答案

有很多选择:

int x = 30;
if (Enumerable.Range(1,100).Contains(x))  //true

事实上，基本的 if 可以在第一次检查中以相反的顺序更优雅地编写:

And indeed basic if more elegantly can be written with reversing order in the first check:

if (1 <= x && x <= 100)   //true

另外，请查看此 SO 帖子，了解正则表达式选项.

Also, check out this SO post for regex options.

注意事项:

• LINQ 解决方案严格用于样式点 - 因为 Contains 迭代所有项目，它的复杂性是 O(range_size) 而不是 O(1)，通常是范围检查所期望的.
  其他范围的更通用版本(注意第二个参数是计数，而不是结束):

• LINQ solution is strictly for style points - since Contains iterates over all items its complexity is O(range_size) and not O(1) normally expected from a range check.
  More generic version for other ranges (notice that second argument is count, not end):

if (Enumerable.Range(start, end - start + 1).Contains(x)

没有&&这样的if解决方案是很有诱惑力的，比如1 <= x <= 100 -看起来很优雅，但在 C# 中会导致语法错误Operator '<=' cannot be applied to operands of type 'bool' and 'int'"

There is temptation to write if solution without && like 1 <= x <= 100 - that look really elegant, but in C# leads to a syntax error "Operator '<=' cannot be applied to operands of type 'bool' and 'int'"

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