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头文件的使用** 把函数原型和常量定义放在一个头文件中是一个很好的编程习惯。例子：假设需要管理4个连锁的旅馆。对于预定住宿时间超过一天的人来说，第1天的收费是第1天的95%，而第3天的收费则是第2天的95%，等待。编写一个程序，对于指定的旅馆和住宿天数可以计算出收费总额。同时程序中要实现一个菜单，从而允许用户反复进行数据输入直到选择退出。源码：/* usehotel.c -- 旅馆房间收费程序 */#include <stdio.h>#include "hotel.h"int main(void){ int nights; double hotel_rate; int code; while ((code = menu()) != QUIT) { switch (code) { case 1: hotel_rate = HOTEL1; break; case 2: hotel_rate = HOTEL2; break; case 3: hotel_rate = HOTEL3; break; case 4: hotel_rate = HOTEL4; break; default: hotel_rate = 0.0; printf("Oops!\n"); break; } nights = getnights(); showprice(hotel_rate, nights); } printf("Thank you and goodbye.\n"); return 0;}/* hotel.c -- 旅馆管理函数 */#include <stdio.h>#include "hotel.h"int menu(void){ int code, status; printf("\n%s%s\n", STARS, STARS); printf("Enter the number of the desired hotel: \n"); printf("1) Fairfield Arms 2) Hotel Olympic\n"); printf("3) Chertworthy Plaza 4) The Stockeon\n"); printf("5) quit\n"); printf("%s%s\n", STARS, STARS); while ((status = scanf("%d", &code)) != 1 || (code < 1 || code > 5)) { if (status != 1) scanf("%*s"); printf("Enter an integer from 1 to 5, please.\n"); } return code;}int getnights(void){ int nights; printf("How many nights are need? "); while (scanf("%d", &nights) != 1) { scanf("%*s"); printf("Please enter an integer, such as 2.\n"); } return nights;}void showprice(double rate, int nights){ int n; double total = 0.0; double factor = 1.0; for (n = 1; n <= nights; n++, factor *= DISCOUNT) total += rate * factor; printf("The total cost will be $%0.2f.\n", total);}/* hotel.h -- hotel.c中的常量定义和函数声明 */#define QUIT 5#define HOTEL1 80.00#define HOTEL2 125.00#define HOTEL3 155.00#define HOTEL4 200.00#define DISCOUNT 0.95#define STARS "*********************"//输出选项列表int menu(void);//返回预定的天数int getnights(void);//按饭店的星级和预定的天数计算价格并显示void showprice(double, int);运行示例：******************************************Enter the number of the desired hotel:1) Fairfield Arms 2) Hotel Olympic3) Chertworthy Plaza 4) The Stockeon5) quit******************************************3How many nights are need? 1The total cost will be $155.00.******************************************Enter the number of the desired hotel:1) Fairfield Arms 2) Hotel Olympic3) Chertworthy Plaza 4) The Stockeon5) quit******************************************4How many nights are need? 3The total cost will be $570.50.******************************************Enter the number of the desired hotel:1) Fairfield Arms 2) Hotel Olympic3) Chertworthy Plaza 4) The Stockeon5) quit******************************************5Thank you and goodbye.程序特色：通过检测scanf()函数的返回值来跳过输入的非数字数据，并前使用scan("%*s")来跳至下一空白字符。在scanf()中，把*放在%和说明符之间使函数跳过相应的输入项目，即相当于没有输入。考察代码： while (scanf("%d", &nights) != 1) { scanf("%*s"); printf("Please enter an integer, such as 2.\n"); }这段代码运用了C的两个运算规则：逻辑表达式从左向右运算，并且一旦结果明显为假，运算会立即停止。在本例中，只有确定scanf()已成功读取了一个整形数组后，变量code才会被检查。 |
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