Check out example codes for "istringstream". It will help you in understanding the concepts better.

Code Example 1

The std::istringstream is a string class object which is used to stream the 
string into different variables and similarly files can be stream into strings.
Objects of this class use a string buffer that contains a sequence of characters. 
This sequence of characters can be accessed as a string object.  

// C++ program to illustrate std::istringstream 
#include <iostream> 
#include <sstream> 
#include <string> 
using std::istringstream; 
using std::string; 
using std::cout; 
int main() 
    // Input string 
    string a("1 2 3"); 
    // Object class of istringstream 
    istringstream my_stream(a); 
    // Variable to store number n 
    int n; 
    // Stream a number till white space is encountered 
    my_stream >> n; 
    cout << n << "\n"; 

Code Example 2

If you include #include <sstream> then you must also reference the class by:

std::stringstream or declare using namespace std; before using it.

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