Question

I am trying to understand how stringstream works in order to be able to identify and convert possible numbers that were inputted as strings… for some reason this small piece of code I wrote to try and understand stringstream is being annoying with a few errors…

#include <iostream>
#include <string>

using namespace std;

int str2int (const string &str) {
  std::stringstream ss(str);
  int num;
  if((ss >> num).fail())
  { 
      num = 0;
      return num;
  }
  return num;
}

int main(){
    int test;
    int t = 0;
    std::string input;
    while (t !=1){
        std::cout << "input: ";
        std::cin >> input;
        test = str2int(input);
        if(test == 0){
            std::cout << "Not a number...";
        }else
            std::cout << test << "\n";
        std::cin >> t;
    }
    return 0;
}

Errors:

Error C2079:'ss' uses undefined class std::basic_stringstream<_elem,_traits,_alloc>'
Error C2228: left of '.fail' must have class/struct/union
Error C2440: 'initializing': cannot convert 'const std::string' into 'int'

what am I doing wrong?

Answer 1

You need to include the following header file –

#include <sstream>

Whenever you see errors like undefined class, you should always look for missing header files first.

Here is the documentation for the stringstream class.