传递多个值切换用逗号分隔值 [英] passing multiple values to switch separating the values by commas

问题描述

我可以传递多个值开关case语句用逗号分隔不同的值？什么会前任pression评估为？如果没有错误，其中多个值将编译器评估与交换机？牢记逗号运算符的低precedence？例如说我写的code如下：

  INT M = 10;
开关（间，间* 2）
{
     案例10：输出（\\ n案件10）;
     案例20：输出（\\ n案件20）;
     案例30：输出（\\ n案件30）;
     默认：输出（\\ n任何情况下）;
 }
 

解决方案

逗号运算符的所有前pressions并返回最右边的值。 （它不会使您使用它在开关任何区别。）

您的例子是完全一样的开关（M * 2），但如果任何preceding前pressions的有副作用，这些侧效果会被执行语句开关之前被应用。

Can I pass multiple values to the switch case statement separating different values by commas ? what would the expression evaluate to? If no error occurs, which of the multiple values would the compiler evaluate the switch with ? Keeping in mind the low precedence of the comma operator? say for instance i write the code as follows:

int m=10;
switch(m, m*2)
{
     case 10: printf("\n case 10");
     case 20: printf("\n case 20");
     case 30: printf("\n case 30");
     default: printf("\n no case");
 }

解决方案

The comma operator evaluates all the expressions and returns the value of the rightmost one. (It doesn't make any difference that you're using it in a switch.)

Your example is exactly the same as switch (m*2), but if any of the preceding expressions had side effects, those side effect would be applied before the switch statement was executed.

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