C ++: reading in arguments with a single istringstream object

Question

int i1;
std::istringstream z(argv[1]);
z >> i1;
cout << i1;
z.str(argv[2]);
int i2;
z >> i2;
cout << i2;

This is my code. My first argument is 123, and the second argument is 12. I expect the result to be 12312. Instead, I see 1234196880. Why? I thought that with the str method, could I reset pass the stream to the second argument and read it?

Answer 1

When you do

z.str(argv[2]);

str (http://www.cplusplus.com/reference/sstream/stringbuf/str/), . , (http://en.cppreference.com/w/cpp/io/basic_istream/seekg)

Answer 2

, istringstream, .

, :

template<typename TargetType>
TargetType convert(const std::string& value) {
    TargetType converted;
    std::istringstream stream(value);
    stream >> converted;
    return converted;
}

, , reset :

int i1 = convert<int>(argv[1]);
int i2 = convert<int>(argv[2]);

: ++ 11, std:: stoi