#include <string>
#include <iostream>
#include <sstream>

void main()
{ while (true)
  { cout << "enter an expression: ";
    string line;
    getline(cin, line);
    cout << "line is '" << line << "'\n";
    istringstream iss(line + " END!");
    string r = "";
    while (true)
    { string s;
      iss >> s;
      if (iss.fail())
        break;
      cout << " partial result: " << s << "\n";
      if (s == "END!")
        break;
      r += s; }
    cout << "result = " << r << "\n"; } }