函数参数设置默认值的用法

如果未传递参数的值，则会使用默认值，如果指定了值，则会忽略默认值

#include <iostream>
using namespace std;
 
int Test_Function_Sum(int a, int b=20)
{
  int result = 0;
 
  result = a + b;
  
  return (result);
}
 
int main ()
{
   int a = 100;
   int b = 200;
   int result = 0;
 
   // 调用函数来添加值
   result = Test_Function_Sum(a, b);
   cout << "Total value is :" << result << endl;
 
   // 再次调用函数
   result = Test_Function_Sum(a);
   cout << "Total value is :" << result << endl;
 
   return 0;
}

/*********************
* 输出的结果：
* Total value is :300
* Total value is :120
*********************/