声明一个有多个默认参数的函数,如
void func(int a,int b=2,int c=3.int d=4);

调用,
func();                      //error
func(12,12);                 //ok
func(2,15,,20);              //error
如此调用错误,是怎样一个从右到左顺序匹配默认的?

got it!多谢~!