input exception try/catch

[mordred2]

I am trying to throw an input error exception when a char is input into an int variable but when i test it with ft=a the program runs some kind of infinite loop.

int main()
{
   char error='a';
   double ft;
   double in;
   double cm;
   int again=0;
   char yn;
   while(again<=0)
   {
      try{
         cout<<"feet: ";
         cin>>ft;
         if(!cin)
            throw error;
         cout<<"inches: ";
         cin>>in;
         if(!cin)
            throw error;
         cout<<"centimeters: ";
         if(ft<0)
            throw -1;
         if(in<0)
            throw -1;
         cm=(12*ft*2.54)+(in*2.54);
         cout<<cm<<endl;
      }
      catch(int)
      {
         cout<<"Error values must be positive."<<endl;
         cout<<"enter new values? y/n"<<endl;
         cin>>yn;
         if(yn=='n')
            again=1;
      }
      catch(...)
      {
         cout<<"Error values must be numeric.";
         cout<<"enter new values? y/n"<<endl;
         cin>>yn;
         if(yn=='n')
            again=1;
      }
   }
system ("PAUSE");
return 0;
}

[long double main]

You never clear cin's error flags, so the input on line 40 will fail, so again doesn't get set to anything, so the loop will run again (with the input continuing to fail).

[mordred2]

how do i fix that?

[long double main]

catch(...)
{
    cin.clear(); // Clear error flags
    cin.ignore(numeric_limits<streamsize>::max(), '\n'); // Clear out the input buffer
    
    cout<<"Error values must be numeric.";
    cout<<"enter new values? y/n"<<endl;
    cin>>yn;
    if(yn=='n')
        again=1;
}

You'll need to #include <limits> as well.

[mordred2]

thank you