stringstream 与空格 (大家讨论一下代码结果的原因)

#include <iostream>     // std::cout, std::endl
#include <iomanip>      // std::setw

 #include <sstream>
int main ()
{ 
    
     char *p1="1   9 ";
     
     std::stringstream stringstr1;
     stringstr1 << p1;
     int id;
     while(!stringstr1.eof())
     {
          stringstr1 >> id;
          std::cout<<id<<std::endl;
      }
      std::cout<< "***************************" <<std::endl;
     char *p2="1   9"; 
     std::stringstream stringstr2;
     stringstr2 << p2;
     while(!stringstr2.eof())
     {
         stringstr2 >> id;
         std::cout<<id<<std::endl;
      }      
      getchar();
  return 0;
}