C++字符串轉數字

bool to_number ( const string& s, int& n ){

    istringstream iss ( s );

    return iss >> n;
}

bool to_number ( const string& s, float& n ){

    istringstream iss ( s );

    return iss >> n;
}

bool to_number ( const string& s, double& n ){

    istringstream iss ( s );

    return iss >> n;
}

int n = 0;
    cout << to_number ( "234", n ) << endl;
    cout << n << endl;

    istringstream iss ( "123.45" );      //字符串輸入流
    double num;

    if ( iss >> num ) 
        cout << num << endl;

    ostringstream oss;
    oss << 543.21;
    string s = oss.str();

    cout << s << endl;