第八章 字符串输入/输出和验证

getchar()和putchar()每次都只能处理一个字符
空格 换行都能读，所以有时候要对数据进行处理

编写一个程序，遇到EOF之前。统计读入的字符

#include 

int main(void)
{
    int count;
 
    while ( getchar() != EOF)
    {
       count++;
    }

    printf("%d", count);

    return 0 ;
}

编写一个程序。读取大小写字母的个数

#include 
#include 

int main(void)
{
    int ch ;
    int Count, count;
 
    while ((ch = getchar()) != EOF)
    {
        if (isalpha(ch))
        {
            if (islower(ch))
            {
                count++;
            }
            else
                Count++;
        }

    }

    printf("大写字母:%d个\n小写字母:%d个", Count, count);

    return 0 ;
}

编写一个程序。把输入作为字符流读取报告平均每个单词的字母数。

#include 
#include 

int main(void)
{
    char ch;
    int letter = 0, word = 0;
    int flag;

    while ( (ch = getchar()) != EOF)
    {
        if (isspace(ch) && flag == 1)
        {
            word++;
            flag = 0;
        }
        else if (isalpha(ch))
        {
            letter++;
            flag = 1;
        }
    }
    printf("单词:%d个, 字母:%d个\n", word, letter);
    printf("平均每个单词%.2lf个字母\n", (double)letter / (double) word);
    

    return 0;
}

修改程序清单8.4的程序

#include 

int main(void)
{
    int enter_;
    int guess = 50;
    char ch;
    int x = 0, y = 100;

    printf("Enter an int from 1 to 100. I will try to guess:\n");
    scanf("%d", &enter_);
    printf("your number %d", guess);

    printf("Uh....is your number %d\n", guess);
    printf("a) 大了            b)小了\n");
    printf("y) yes\n");
    getchar();
    while ((ch = getchar()) != 'y')
    {
    
    if (ch == 'a')
    {
        y = guess; 
        guess = (guess - x) / 2 + x;

    }
    else if (ch == 'b')
    {
        x = guess;  
        guess = (y - guess) / 2 + guess;
        
    }

    
    printf("Uh....is your number %d\n", guess);
    printf("a) 大了            b)小了\n");
    printf("y) yes\n");
 
    while (getchar() != '\n')
    {
        continue;
    }
    

    } 
    
    printf("厉害吧！！！");

    return 0;
}

修改程序清单8.8中的get_first()函数，让该函数返回读取的第一个非空白字符，并在一个简单的程序中测试

#include 
#include 

void get_first(void);

int main(void)
{
    get_first();

    return 0;
}

void get_first(void)
{
    int ch;
    
    while ( isspace(ch = getchar()))
    {
        continue;
    }
    while (getchar() != '\n')
    {
        continue;
    }
    printf("%c", ch);
    
}

修改第7章的编程练习8，用字符代替数字标记菜单的选项。用q代替5作为结束输入的标记

#include 
#include 

#define AMT1 300
#define AMT2 150
#define OVERTIME 1.5
#define TIME 40
#define TAX15 0.15
#define TAX20 0.20
#define TAX25 0.25
#define SIGN "***********************************"

char get_choice(void);
char get_first(void);
float get_time(void);
float money(float mon_hr);

int main(void)
{
    char ch;

    while ((ch = get_choice()) != 'q')
    {
        switch (ch)
        {
        case 'a':
            money(8.75);
            break;
        case 'b':
            money(9.33);
            break;
        case 'c':
            money(10.00);
            break;
        case 'd':
            money(11.20);
            break;

        default:
            printf("Enter a, b, c, d, q");
            break;
        }
    }
    
    return 0;
}

char get_choice(void)
{
    int ch;

    printf("%s%s\n", SIGN, SIGN);
    printf("Enter the number corresponding to the desired pay rate or action:\n");
    printf("a) $8.75/hr            b) $9.33/hr\n");
    printf("c) $10.00/hr           d) $11.20/hr\n");
    printf("q) quit\n");
    printf("%s%s\n", SIGN, SIGN);
    ch = get_first();

    return ch;
}

char get_first(void)
{
    int ch;

    while (isspace(ch = getchar()))
    {
        continue;
    }
    while (getchar() != '\n')
    {
        continue;
    }
    
    return ch;
}

float money(float mon_hr)
{
    float time, gross, taxes, net;
    time = get_time();
    gross = time * mon_hr;
    if (gross <= AMT1)
    {
        taxes = TAX15 * gross;
    }
    else if (gross <= AMT1 + AMT2)
    {
        taxes = TAX15 * AMT1 + (gross - AMT1) * TAX20;
    }
    else
    {
        taxes = TAX15 * AMT1 + TAX20 * AMT2 + TAX25 * (gross - AMT1 - AMT2);
    }
    
    net = gross - taxes;

    printf("gross: $%.2lf; taxes: $%.2lf; net: $%.2lf.\n", gross, taxes, net);
}

float get_time(void)
{
    float time;
    char ch;
    printf("Enter time:");
    while ((scanf("%f", &time)) != 1)
    {
        while ((ch = getchar()) != '\n')
            putchar;
        printf(" is not number:\n");
    }
    if (time > TIME)
    {
        time = TIME + (time - TIME) * OVERTIME;
    }

    return time;
}

编写一个程序，显示一个提供加法、减法、乘法、除法的菜单。获得用户选择的选项后，程序提示用户输入两个数字，让后执行用户刚才选择的操作。改程序只接受菜单提供的选项。

#include 
#include 

char get_first(void);           //获得一个字符
char get_choice(void);          //选择语句
void add(void);                 //加法
void subtract(void);            //减法
void multiply(void);            //乘法
void divide(void);              //除法
float get_float(void);        //获得数字

int main(void)
{
    char ch;

    while ((ch = get_choice()) != 'q')
    {
        switch (ch)
        {
            case 'a':
                add();
                break;
            case 's':
                subtract();
                break;
            case 'm':
                multiply();
                break;
            case 'd':
                divide();
                break;

            default:
                printf("Please respond with a, s, m, d, q.\n");
        }
    }




    return 0;
}

char get_choice(void)
{
    int ch;
    printf("Enter the operation of your choice:\n");
    printf("a. add              s. subtract\n");
    printf("m. multiply         d. divide\n");
    printf("q. quit\n");
    ch = get_first();
    return ch;
    
}

char get_first(void)
{
    int ch;

    while (isspace(ch = getchar()))
    {
        continue;
    }
    while (getchar() != '\n')
    {
        continue;
    }
    
    return ch;
}

void add(void)
{
    float x, y;
    printf("Enter first number:");
    x = get_float();
    printf("Enter seconde number:");
    y = get_float();
    printf("%.1f + %.1f = %.1f\n", x, y, x+y);

}

void subtract(void)
{
    float x,y;
    printf("Enter first number:");
    x = get_float();
    printf("Enter seconde number:");
    y = get_float();
    printf("%.1f - %.1f = %.1f\n", x, y, x-y);
}

void multiply(void)
{
    float x,y;
    printf("Enter first number:");
    x = get_float();
    printf("Enter seconde number:");
    y = get_float();
    printf("%.1f * %.1f = %.1f\n", x, y, x*y);
}

void divide(void)
{
    float x,y;
    printf("Enter first number:");
    x = get_float();
    printf("Enter seconde number:");
    while ((y = get_float()) == 0)
        continue;
    printf("%.1f / %.1f = %.1f\n", x, y, x/y);
}

float get_float(void)
{
    float input;
    char ch;
    while((scanf("%f", &input)) != 1)
    {
        while ((ch = getchar()) != '\n')
            putchar(ch);
        printf(" is not an number\n");
    }

    return input;
}