a problem about istream

[zzvsst]

hi, i'm reading the chapter on "standard IO library". And i copied below codes, with some little changes, to my IDE.

#include<iostream>

using namespace std;

int main()
{
	int ival;

	while(cin >> ival, !cin.eof())
	{		
		if(cin.good())
		{
			cout << ival << endl;
			continue;
		}
		else
		{
			cout << "error, please input again!" << endl;
			cin.clear(istream::failbit);
			continue;
		}
	}

	return 0;
}

When i run it. if i input an int value, it's OK. but if i input some other type data, such as "!", disaster happens. it will display "error, please input again!" ceaselessly. So i have no chance to input next data. How could this happen?

As i'm a newbie to C++, so would you please explain as explicitly as possible? Gneral explanation is also OK. I'd appreciate anyone's help.

[kbw]

If the stream goes bad, you have to manually change the state back to good.
cin.setstate(std::ios::good);

Also, don't check for eof. When end of file is detected, the stream changes state (to bad or fail, I can't remember).

[zzvsst]

@kbw

Thanks for your help. But i have tried to
replace
cin.clear(istream::failbit);
with
cin.setstate(cin.good());

The output is the same.

error, please input again!
error, please input again!
error, please input again!
error, please input again!
error, please input again!
......

And i also tried cin.clear(), it doesn't help either.
any further suggestion?
Thank you.

[zzvsst]

Some additional information:

I try to use

cin.setstate(cin.good());
cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n'); 

to manually change the state to good and empty the buffer.
It also fails.

[Bazzy]

try

cin.clear();
cin.ignore(numeric_limits<streamsize>::max(), '\n');

[btripp]

what bazzy posted should work. I think you have a dangling new line. I had a simaler problem a while back and used code similar to what bazzy suggested.

[zzvsst]

Thanks to Bazzy and btripp.
I have tried what Bazzy posted. It works very well.
And now I know the difference between cin.setstate() and cin.clear().