/*练习—03|函数y=f(x)可表示为：y=2x+1(x<0),y=0 (x=0),y=2x-1 (x>0).*/

#include <stdio.h>
#include <stdlib.h>
int main()
 4  {
    double x, y;
    int i;

    do{
        printf ("请输入一个x值:");
        scanf ("%lf", &x);

        if (x < 0)
            {y = 2 * x + 1;
             printf("y = %.2lf\n",y);
      }
        if (x == 0)
            {y = 0;
             printf("y = %.2lf\n",y);
      }
        if (x > 0)
            {y = 2 * x - 1;
             printf("y = %.2lf\n",y);
      }
        else
            printf("您输入的是数字吗？\n");
        printf("----------------------\n");
        printf("是否想重新输入一个x的值？\n");
        printf("Yes ----按数字键【1】\n");
        printf("No  ----按数字键【0】\n");
        scanf ("%d",&i);
   }
       while (i == 1);
       return 0;
34   }