Converting Infix to Postfix

typedef fsu::Queue < token > tokenQueue;
typedef fsu::Stack < token > tokenStack;

int i2p (tokenQueue & Q1, tokenQueue & Q2)
// converts infix expression in Q1 to postfix expression in Q2
{
   tokenStack S;
   Q2.Clear();
   while (!Q1.Empty())
   {
      if (Q1.Front() == '(')
      // push '(' to mark beginning of a parenthesized expression
      {
         S.Push(Q1.Front());
         Q1.Pop();
      }
      else if (Q1.Front().Operator())
      {
         // pop previous operators of equal or higher precedence to output
         while (!S.Empty() && S.Top() >= Q1.Front())
         {
            Q2.Push(S.Top());
            S.Pop();
         }
         // then push new operator onto stack
         S.Push(Q1.Front());
         Q1.Pop();
      }
      else if (Q1.Front() == ')')
      // regurgitate operators for the parenthesized expression
      {
         while (!S.Empty() && !(S.Top() == '('))
         {
            Q2.Push(S.Top());
            S.Pop();
         }
         if (S.Empty())      // unbalanced parentheses
         {
            cout << "** error: too many right parens\n";
            return 0;
         }
         S.Pop();            // discard '('
         Q1.Pop();           // discard ')'
      }
      else                   // t should be an operand
      // send operand directly to output
      {
         Q2.Push(Q1.Front());
         Q1.Pop();
      }
   }  // end while()
   // regurgitate remaining operators
   while (!S.Empty())
   {
      if (S.Top() == '(')      // unbalanced parentheses
      {
         cout << "** error: too many left parens\n";
         return 0;
      }
      Q2.Push(S.Top());
      S.Pop();
   }
   return 1;
}  // end i2p()