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What's the problem of the flowing program? RRS feed

  • 问题

  • what's the problem of the flowing program?

    #include<iostream>
    #include<iomanip>
    #include<cmath>
    using namespace std;
    double f(double);
    double xpoint(double,double);
    double root(double);
    int main()
    {
     double x1,x2,f1,f2,x;
     do
     {
      cout<<"input x1,x2: ";
      cin>>x1>>x2;
      f1=f(x1);
      f2=f(x2);
     }
     while(f1*f2>=0);
     cout<<setiosflags(ios::fixed)<<setprecision(7);

     cout<<"A root is: "<<x<<endl;

     return 0;
    }
    double f(double x)
    {
     double y;
     y=x*x*x-5*x*x+16*x-80;
     return y;
    }
    double xpoint(double x1,double x2)
    {
     double y;
     y=(x1*f(x2)-x2*f(x1))/(f(x2)-f(x1));
     return y;
    }
    double root(double x1,double x2)
    {
     double y1,y,x;
     y1=f(x1);
     do
     {
      x=xpoint(x1,x2);
      y=f(x);
      if(y*y1>0)
      {
       y1=y;
       x1=x;
      }
      else
       x2=x;
     }
     while(fabs(y)>=0.00001);
     return x;
    }

         

    2011年8月2日 17:21

答案

  • variable 'x' used without having been initialized and referenced.
    Visual C++ enthusiast, like network programming and driver development. At present is being engaged in the WinCE/Windows Mobile platform embedded development.
    • 已标记为答案 Rob Pan 2011年8月9日 9:57
    2011年8月3日 3:31
    版主