#include "stdio.h"
double fnfun(double x);
double fnfun(double x)
{ double y;
    if(x>1)
        y=x*x+1;
      else if(-1<=x&&x<=1)
            y=x*x;
          else if(x<-1)
                y=x*x-1;
    return y;

            

}

void main()
{ double x,result;
    printf("please input x:");
    scanf("%f",&x);
    result=fnfun(x);
    printf("y=%f",result);
    getch();

}

为什么X输入任何值。。求得的Y都是0.00000