函数缺省

#include <iostream>//函数参数的缺省
using namespace std;

int sum(int i=-1,int j=2);
int main()

{
    int a=5,b=7;
    cout<<sum(a,b)<<endl;
    cout<<sum(a)<<endl;
    cout<<sum()<<endl;

    return 0;
}

int sum(int i,int j)
{
return i+j;

}