传递多个值以切换以逗号分隔值 [英] passing multiple values to switch separating the values by commas

问题描述

我可以将多个值传递给用逗号分隔不同值的 switch case 语句吗?表达式的计算结果是什么?如果没有发生错误，编译器将使用多个值中的哪一个来评估开关?记住逗号运算符的低优先级?比如说我写代码如下:

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("
 case 10");
     case 20: printf("
 case 20");
     case 30: printf("
 case 30");
     default: printf("
 no case");
 }

推荐答案

逗号运算符计算所有表达式并返回最右边的值.(在 switch 中使用它没有任何区别.)

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.)

您的示例与 switch (m*2) 完全相同，但如果前面的任何表达式有副作用，则这些副作用将在 switch 语句已执行.

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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