函数和结构

//传递返回结构
////////////////////////////////////////////////////////////////////////////////////
#include<iostream>
struct str_times
{
 int hours;
 int mins;
};
const int mins_per_hr=60;
str_times sum(str_times t1,str_times t2);
void show_time(str_times t);

int main()
{
 using namespace std;
 str_times day1={5,45};
 str_times day2={4,55};

 str_times trip=sum(day1,day2);
 cout<<"two-day total: ";
 show_time(trip);

 str_times day3={4,32};
 cout<<"three-day total: ";
 show_time(sum(trip,day3));
 return 0;
}

str_times sum(str_times t1,str_times t2)
{
 str_times total;

 total.mins=(t1.mins+t2.mins)%mins_per_hr;
 total.hours=t1.hours+t2.hours+(t1.mins+t2.mins)/mins_per_hr;

 return total;
}

void show_time(str_times t)
{
 using namespace std;
 cout<<t.hours<<" hours, "
  <<t.mins<<" minutes\n";
}







//传递结构地址
 ////////////////////////////////////////////////////////////////////////////////////////
#include <iostream>
#include <cmath>
//structure  templates
struct polar
{
 double distance;
 double angle;
};
struct rect
{
 double x;
 double y;
};
//prototypes
void rect_to_polar(const rect * pxy,polar * pda);
void show_polar(const polar * pda);

int main()
{
 using namespace std;
 rect rplace;
 polar pplace;

 cout<<"enter the x and y values: ";
 while(cin>>rplace.x>>rplace.y)
 {
         rect_to_polar(&rplace,&pplace);
   show_polar(&pplace);
   cout<<"next two num(q to out): ";
 }
 cout<<"done!"<<endl;
    return 0;
}

//show st
void rect_to_polar(const rect * pxy,polar * pda)
{
 using namespace std;
 pda->distance=
  sqrt(pxy->x*pxy->x+pxy->y*pxy->y);
 pda->angle=atan2(pxy->y,pxy->x);//atan2 根据 x y 值计算角度
}

void show_polar(const polar * pda)
{
 using namespace std;
 const rad_to_deg=57.29577951;

 cout<<"distance= "<<pda->distance;
 cout<<", angel="<<pda->angle*rad_to_deg;
 cout<<"degrees\n";
}