帮忙看下这段代码，明明照着书做的，怎么没现象呢？

C/C++ code

using namespace std;istream &get (istream &in){    int val;    while (in >> val, !in.eof())    {        if (in.bad())        {            break;        }        if (in.fail())        {            cerr<<"ERROR"<<endl;            in.clear();            in.ignore(200,' ');            continue;        }    }    in.clear();    return in;}int main(){    int vv;    get(cin);    cin>>vv;    cout<<vv<<endl;        return 0;}

C/C++ code

using namespace std;int get (istream &in){    int val;    while (in >> val, !in.eof())    {        if (in.bad())        {            break;        }        if (in.fail())        {            cerr<<"ERROR"<<endl;            in.clear();            in.ignore(200,' ');            continue;        }    }    in.clear();    return val;}int main(){    int vv = get(cin);    cout<<vv<<endl;    return 0;}
[解决办法]
C/C++ code
int get (istream &in){    int val;    while (in >> val, !in.eof())    {        if (in.bad())        {            break;        }        if (in.fail())        {            cerr<<"ERROR"<<endl;            in.clear();            in.ignore(200,' ');            continue;        }    }    in.clear();    return val;}int main(){    cout<<get(cin)<<endl;    return 0;}
[解决办法]
探讨


书上写 cin>> vv 这句话是重新使用流，这是什么意思？