参数缺省值只能出现在函数的声明中，而不能出现在定义体中

参数缺省值只能出现在函数的声明中，而不能出现在定义体中 。 

#include <iostream>

/* run this program using the console pauser or add your own getch, system("pause") or input loop */
using namespace std;
//声明函数模板的原型语句
template <class T> void swap(T *x, T *y);

//定义一个结构类型
struct student {
    int n;
    char name[20];
    float grade;
};

int main(int argc, char** argv) {
        //交换两个int型变量中的数据
    int m=3,n=5;
    cout<<"m="<<m<<"  n="<<n<<endl;
    swap(&m,&n);
    cout<<"m="<<m<<"  n="<<n<<endl;
    cout<<"-------------------"<<endl;

    //交换两个double型变量中的数据
    double x=3.5,y=5.7;
    cout<<"x="<<x<<"  y="<<y<<endl;
    swap(&x,&y);
    cout<<"x="<<x<<"  y="<<y<<endl;
    cout<<"-------------------"<<endl;

    //交换两个char型变量中的数据
    char c1='A',c2='a';
    cout<<"c1="<<c1<<"  c2="<<c2<<endl;
    swap(&c1,&c2);
    cout<<"c1="<<c1<<"  c2="<<c2<<endl;
    cout<<"-------------------"<<endl;

    //交换两个结构变量中的数据
    student s1={1001,"ZhangHua",90};
    student s2={1011,"LiWei",95.5};
    cout<<"s1:  ";
    cout<<s1.n<<"  "<<s1.name<<"  "<<s1.grade<<endl;
    cout<<"s2:  ";
    cout<<s2.n<<"  "<<s2.name<<"  "<<s2.grade<<endl;

    swap(&s1,&s2);
    cout<<"swap(s1,s2):"<<endl;
    cout<<"s1:  ";
    cout<<s1.n<<"  "<<s1.name<<"  "<<s1.grade<<endl;
    cout<<"s2:  ";
    cout<<s2.n<<"  "<<s2.name<<"  "<<s2.grade<<endl;
    return 0;
}



//定义名为swap的函数模板用于交换两个变量中的数据
template <class T> void swap(T *x, T *y)
{
    T temp;
    temp=*x;
    *x=*y;
    *y=temp;
}