结构：结构中的结构

结构数组

struct date dates[100];
struct date dates[] = {
    {4,5,2005},{2,4,2005}
}

#include<stdio.h>

struct time {
    int hour;
    int minutes;
    int seconds;
};

struct time timeUpdate(struct time now);

int main(int argc, char const *argv[])
{
    struct time testTimes[5] = {
        {11,59,59},{12,0,0},{1,29,59},{19,12,27}
    };
    int i;

    for( i=0; i<5; ++i){
        printf("Time is %.2i:%.2i:%.2i", testTimes[i].hour, testTimes[i].minutes, testTimes[i].seconds);

        testTimes[i] = timeUpdate(testTimes[i]);

        printf("...one second later it's %.2i:%.2i:%.2i\n", testTimes[i].hour, testTimes[i].minutes, testTimes[i].seconds);
    }

    return 0;
}

struct time timeUpdate(struct time now)
{
    ++now.seconds;
    if ( now.seconds == 60 ) {
        now.seconds = 0;
        ++now.minutes;

        if ( now.minutes == 60 ){
            now.minutes = 0;
            ++now.hour;

            if( now.hour == 24){
                now.hour = 0;
            }
        }
    }

    return now;
}

Time is 11:59:59...one second later it's 12:00:00
Time is 12:00:00...one second later it's 12:00:01
Time is 01:29:59...one second later it's 01:30:00
Time is 19:12:27...one second later it's 19:12:28
Time is 00:00:00...one second later it's 00:00:01

结构中的结构

struct dataAndTime{
    struct date sdate;
    struct time stime;
};

嵌套的结构

struct point {
    int x;
    int y;
};
struct rectangle {
    struct point pt1;
    struct point pt2;
}
如果有变量
    struct rectangle r;
就可以有：
    r.pt1.x和r.pt1.y,
    r.pt2.x和r.pt2.y

如果有变量定义
    struct rectagle r,*rp;
    rp = &r;
那么下面的四种形式是等价的：
    r.pt1.x
    rp->pt1.x
    (r.pt1).x
    (rp->pt1).x
但是没有rp->pt1->(因为pt1不是指针)