How Can I Efficiently Check if a Variable Matches Multiple Values in Different Programming Languages?

Elegantly handle multi-valued conditional judgments

Many programming languages ​​provide conditional statements to evaluate whether a variable meets one or more conditions. When you need to check whether a variable meets a specific condition, you usually use multiple if statements nested, for example:

<code>if (value == 1) {
    // value为1时执行的代码
} else {
    if (value == 2) {
        // value为2时执行的代码
    }
}</code>

This approach can become verbose and difficult to maintain when multiple values ​​need to be matched. In SQL, this problem can be solved concisely using the IN operator:

WHERE value IN (1, 2)

In order to implement similar functions in common programming languages, developers usually use some clever tricks or extend the basic library. For example, you can use an array:

if (new[] { 1, 2 }.Contains(value)) {
    // value为1或2时执行的代码
}

Another solution is to define an extension method:

public static bool In<T>(this T obj, params T[] args) {
    return args.Contains(obj);
}

Using this extension method, you can write like this:

if (1.In(1, 2)) {
    // value为1或2时执行的代码
}

These techniques provide a more elegant way to express conditional checks on multiple values, improving code readability and maintainability.

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