流控制中的一个奇怪问题（cin.clear( )）

shawjg

正在学c＋＋，看c＋＋primer
第八章中的一个事例程序：
int main(){
        int ival;
        while(cin>>ival, !cin.eof()){
                if(cin.bad())throw runtime_error("IO stream corrupted");
                if(cin.fail()) {
                        cerr<<"Bad data, try again";
                        cin.clear();
                        continue;
                cout<<ival<<endl;
                }
        }
}

./a.out
a
Bad data, try againBad data, try againBad data, try againBad data, try againBad data, try againBad data, try againBad data, try againBad data, try againBad data, try againBad data, try againBad data, try againBad data, try againBad data, try againBad data, try againBad data, try againBad data, try againBad data, try againBad data, try againBad data, try againBad data, try againBad data, try againBad data, try againBad data, try againBad data, try againBad data, try againBad data, try againBad data, try againBad data, try againBad data, try againBad data, try againBad data, try againBad data, try againBad data, try againBad data, try againBad data, try againBad data, try againBad data, try againBad data, try againBad data, try againBad data, try againBad data, try againBad data, try againBad data, try againBad data, try againBad data, try againBad data, try againBad data, try againBad data, try againBad data, try againBad data, try againBad data, try againBad data, try againBad data, try againBad data, try againBad data, try againBad data, try againBad data, try againBad data, try againBad data, try againBad data, try againBad data, try

输入非数字字符，程序怎么进入死循环了，奇怪。
哪位能指点一下吗？先谢谢了！

shawjg

google了一下，找到原因了。