为什么C ++要求在switch语句中中断? [英] Why does C++ require breaks in switch statements?

问题描述

在用C ++编写 switch 语句时，似乎有必要在每个 case 之后添加一个 break .否则，代码将继续遇到下一种情况.

When writing switch statements in C++, it seems necessary to include a break after every case. Otherwise, the code will continue to run into the next case.

例如:

int x = 1;
switch (x)
{
    case 0:
        std::cout << "x is 0." << std::endl;
    case 1:
        std::cout << "x is 1." << std::endl;
    case 2:
        std::cout << "x is 2." << std::endl;
    default:
        std::cout << "x is neither 0, 1 nor 2." << std::endl;
}

会返回:

>> x is 1.
>> x is 2.

但是:

int x = 1;
switch (x)
{
    case 0:
        std::cout << "x is 0." << std::endl;
        break;
    case 1:
        std::cout << "x is 1." << std::endl;
        break;
    case 2:
        std::cout << "x is 2." << std::endl;
        break;
    default:
        std::cout << "x is neither 0, 1 nor 2." << std::endl;
        break;
}

会返回:

>> x is 1.

我的问题是:如果必须在每个 case 中都包含 break ，那么为什么C ++要求完全将其明确编写?为什么在C ++中默认情况下，为什么不只是在每个 case 之后 break switch 语句呢?有没有可能实际上不希望这种行为的示例?

My question is: If it is necessary to include the break for every case, then why does C++ require it to be explicitly written at all? Why not just break the switch statement after every case by default in C++? Are there any examples when this behaviour may not in fact be desired?

推荐答案

这是为了解决所有问题":

This is for the favour of "falling throught" cases:

switch (x)
{
    case 0:
    case 1:
        std::cout << "x is 0 or 1." << std::endl;
        break;
}

在此示例中，如果x为0或1，则执行case语句.

In this example, the case statement is executed if x is either 0 or 1.

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