text: 
  #include <iostream>
  using namespace std;
  #include <sstream>
  #include <string>
  
  void f(int a)
  {
      cout << "f1\n";
  }
  void f(bool a)
  {
      cout << "f2\n";
  }
  void f(void* a)
  {
      cout << "f3\n";
  }
  
  int main(){
      f(0);
      // f(NULL);  error: call to 'f' is ambiguous
      f(nullptr);
  
      {
         
          string s;
          istringstream ss("1 2 3 4");
          while(ss >> s) cout<<s;
      }
      return 0;
  }