Thread: what's wrong with this? neverending loop

hi, trying to make a small block of code for trapping input errors, I wrote this:


#ifdef HAVE_CONFIG_H
#include <config.h>
#endif
#include <iostream.h>
#include <stdlib.h>

int main(int argc, char *argv[])
{

int pirla;
do
{
cout << "Inserisci un valore intero: ";
cin >> pirla;
}
while (cin.good() == false);
cout << "Il valore di pirla e' " << pirla << endl;
return EXIT_SUCCESS;
}

but if the input is wrong the do...while loop never ends keeping outputting the prompt.
why this happens? how can I put that to work?
thanks and... mercy for the newbie!

I think you have to call cin.clear() after any call to cin.good() or cin.fail(). I can't explain why, something about a fail bit that needs to be cleared. If it isn't cleared cin won't accept input the second time around so good() fails and away you go. I would probably use a flag to get around this, although there are probably other ways as well. I would try this


char flag = 'y';

do
{
cout << "Inserisci un valore intero: ";
cin >> pirla;
if(cin.good())
{
cin.clear();
flag = 'n';
}
else
{
cin.clear();//this may not be necessary but I'd try it this way first
cout << "error. try again." << endl;
}
while (flag == 'y');
cout << "Il valore di pirla e' " << pirla << endl;