C primer plus第14章(结构和其他数据形式)

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//结构体与指针#include <stdio.h>#define LEN 20//#include <console.h> //mac下需要struct names{    char first[LEN];    char last[LEN];};struct guy{    struct names handle;    char favfood[LEN];    char job[LEN];    float income;};int main(void){    struct guy fellow[2] =    {        {   {"Ewen","Villard"},            "grilled salmon",            "personality coach",            58112.00        },        {   {"Rodney","Swillbelly"},            "tripe",            "tabloid editor",            232400.00        }    };    struct guy * him;//这是一个指向结构的指针    printf("address #1:%p #2:%p\n",&fellow[0],&fellow[1]);    //结构与数组不同，需要用取地址符（&）取地址    him = &fellow[0];//告诉该指针它要指向的地址    printf("pointer #1: %p #2:%p\n",him,him+1);    //用指针获取结构的值用->运算符    //him->income等同于fellow[0].income 等同于(*him).income    printf("him->income is $%.2f:(*him) .income is $%.2f\n",him->income,(*him).income);    him++;//指向下一个结构    printf("him->favfood is %s:him->handle.last is %s\n",him->favfood,him->handle.last);    return 0;    //如果him是指向名为barnery的结构的指针    //barney.income == (*him).income == him->income}

//如果要在结构内声明指针而不是数组（指针只保存地址，如果声明数组则保存的是实际的值）struct names{    char *fname;    char *lname;    int letters;};void getinfo(struct namect *pst) {    char temp[81];    printf("Please enter your first name.\n");    gets(temp);    //分配用来存放值的内存（用完别忘记free）    pst->fname = (char*)malloc(strlen(temp) + 1);    //把名字复制到已分配的内存中    strcpy(pst->fname,temp);    printf("Please enter your last name.\n");    gets(temp);    //分配用来存放值的内存（用完别忘记free）    pst->lname = (char*)malloc(strlen(temp) + 1);    //把名字复制到已分配的内存中    strcpy(pst->lname,temp);}

复合文字结构体readfirst = (struct book) {"dadsa","dsasadsa",9.99}

//伸缩型数组成员#include <stdio.h>#include <stdlib.h>struct flex{    int count;    double average;    double scores[];//伸缩型数组成员};void showFlex(const struct flex *p);int main(void){    struct flex * pf1,*pf2;    int n = 5;    int i;    int tot = 0;    //为结构和数组分配存储空间    //为结构分配存储空间sizeof(struct flex)    //为数组分配存储空间n * sizeof(double)    pf1 = malloc(sizeof(struct flex) + n * sizeof(double));    pf1->count = n;    for(i=0; i<n; i++)    {        pf1->scores[i] = 20.0 - i;        tot += pf1->scores[i];    }    pf1->average = tot / n;    showFlex(pf1);    n= 9;    tot = 0;    pf2 = malloc(sizeof(struct flex) + n * sizeof(double));    pf2->count = n;    for(i=0; i<n; i++)    {        pf2->scores[i] = 20.0 - i/2.0;        tot += pf2->scores[i];    }    pf2->average = tot / n;    showFlex(pf2);    free(pf1);    free(pf2);    return 0;}void showFlex(const struct flex *p){    int i;    printf("Scores:");    for(i=0; i<p->count; i++)    {        printf("%g ",p->scores[i]);    }    printf("\nAverage:%g\n",p->average);}

将结构写入文件保存

#include <stdio.h>#include <stdlib.h>#define MAXTITL 40#define MAXAUTL 40#define MAXBKS 10 //图书最多的本书//建立book模板struct book{    char title[MAXTITL];    char author[MAXAUTL];    float value;};int main(void){    struct book library[MAXBKS];//结构数组    int count = 0;    int index,filecount;    FILE *pbooks;    int size = sizeof(struct book);    //以二进制的追加模式打开文件    if((pbooks = fopen("book.dat","a+b")) == NULL)    {        fputs("Can`t open book.dat file\n",stderr);        exit(1);    }    //定位到文件开始处    rewind(pbooks);    //读取并输出文件中已经存在的数据    while(count < MAXBKS && fread(&library[count],size,1,pbooks) == 1)    {        if(count == 0)        {            puts("Current contents of book.dat");        }        printf("%s by %s:$%.2f\n",library[count].title,library[count].author,library[count].value);        count++;    }    filecount = count;    //如果文件存储已满    if(count == MAXBKS)    {        fputs("The book.dat file is full.",stderr);        exit(2);    }    //如果文件还能存储    puts("Please add new book titles.");    puts("Press [enter] at the start of a line to stop.");    //录入新的图书    while(count <MAXBKS && gets(library[count].title) != NULL && library[count].title[0] != '\0')    {        puts("Now enter the author.");        gets(library[count].author);        puts("Now enter the value.");        //下标递增        scanf("%f",&library[count++].value);        //清空输入行        while(getchar() != '\n')        {            continue;        }        //如果未大于最大存储数量，提示输入下一本        if(count< MAXBKS)        {            puts("Enter the next title");        }    }    //写入文件    if(count > 0)    {        puts("Here is the list of your books:");        for(index = filecount; index < count; index++)        {            printf("%s by %s:$%.2f\n",library[index].title,library[index].author,library[index].value);            //count-filecount 本次写入数量（本次写入后总数-写入前总数）            fwrite(&library[filecount],size,count-filecount,pbooks);        }    }    else    {        puts("No books? Too bad.\n");    }    puts("Bye.\n");    fclose(pbooks);    return 0;}

函数指针

#include <stdio.h>#include <stdlib.h>#include <ctype.h>char showmenu(void);void eatline(void);//读至行末void show(void(*fp)(char *),char * str);void ToUpper(char *);   //把字符串转换为大写void ToLower(char *);   //把字符串转换为小写void Transpose(char *);  //大小写专置void Dummy(char *);     //不改变字符串int main(void){    char line[81];    char copy[81];    char choice;    void(*pfun)(char *);//指向一个函数，该函数接受一个char*参数，并且没有返回值    puts("Enter astring(empty line to quit):");    while(gets(line) != NULL && line[0] != '\0')    {        while((choice = showmenu()) != 'n')        {            //用switch语句用来设置指针赋值不同的函数地址            switch(choice)            {            case 'u':                pfun = ToUpper;                break;            case 'l':                pfun = ToLower;                break;            case 't':                pfun = Transpose;                break;            case 'o':                pfun = Dummy;                break;            }            strcpy(copy,line);//为show（）制作一份拷贝            show(pfun,copy);//使用用户选择的函数        }        puts("Enter astring(empty line to quit):");    }    puts("Bye!");    return 0;}char showmenu(void){    char ans;    puts("Enter menu choice:");    puts("u)uppercase l)lowercase");    puts("t)transposed case o)original case");    puts("n)next string");    ans = getchar();            //获取用户的响应    ans = tolower(ans);         //转换为小写    eatline();                  //删除行中剩余部分    while(strchr("ulton",ans) == NULL)    {        puts("Please enter a u,l,t,o, or n:");        ans = tolower(getchar());        eatline();    }    return ans;}void eatline(void){    while(getchar()!= '\n')    {        continue;    }}void ToUpper(char * str){    while(*str)    {        *str = toupper(*str);        str++;    }}void ToLower(char * str){    while(*str)    {        *str = tolower(*str);        str++;    }}void Transpose(char * str){    while(*str)    {        if(islower(*str))        {            *str = toupper(*str);        }        else if(isupper(*str))        {            *str = tolower(*str);        }        str++;    }}void Dummy(char * str){    //不改变字符串}void show(void(*fp)(char*),char * str){    (*fp)(str);//把用户选择的函数作用于str    puts(str);//显示结果}