8_8 menuette.c

8_8 menuette.c -- 菜单程序

#include <stdio.h>
char get_choice(void);
char get_first(void);
int get_int(void);
void count(void);
int main(void)
{
    int choice;
    void count(void);

    while ((choice = get_choice()) != 'q')
    {
        switch (choice)
        {
            case 'a':
                printf("Buy low, sell high.
");
                break;
            case 'b':
                putchar('a');                 /* ANSI  */
                break;
            case 'c':
                count();
                break;
            default:
                printf("Program error!
");
                break;
        }
    }
    printf("Bye.
");

    return 0;
}

void count(void)
{
    int n, i;

    printf("Count how far? Enter an integer:
");
    n = get_int();
    for (i = 1; i <= n; i++)
        printf("%d
", i);
    while (getchar() != '
')
        continue;
}

char get_choice(void)
{
    int ch;
    printf("Enter the letter of your choice:
");
    printf("a. advice         b. bell
");
    printf("c. count          d. quit
");
    ch = get_first();
    while ((ch < 'a' || ch > 'c') && ch != 'q')
    {
        printf("Please respond with a, b, c, or q.
");
        ch = get_first();
    }

    return ch;
}

char get_first(void)
{
    int ch;
    ch = getchar();
    while (getchar() != '
')
        continue;

    return ch;
}

int get_int(void)
{
    int input;
    char ch;

    while (scanf("%d", &input) != 1)
    {
        while ((ch = getchar()) != '
')
            putchar(ch);   // 处理错误输出
        printf(" is not an integer.
Please enter an ");
        printf("integer value, such as 25, -178, or 3: ");
    }

    return input;
}