Thread: parser problem.

I tried to change this parser which was using cin to use stringstream..
when was using cin, everything was going perfectly..
but now if I enter any expression like : 4+5 it'll get stuck on the first char (4 in this exemple..)

But I changed really few things..
added stringstream ist(temp_string);
and then I changed all cin for ist..

Do you guys see anything wrong there?

Code:

Token_value get_token()
{
      stringstream ist(temp_string);
      char ch = 0;
      do {			// skip whitespace except '\n'
	 if(!ist.get(ch)) return curr_tok = END;
      }while (ch != '\n' && isspace(ch));
      switch (ch)
      {
	  case 0 : case  'E':
	        return curr_tok=END;
	  case ';' :	return curr_tok = PRINT;
	  case '\n' :	line_count.new_line();
	  case '*' :
	  case '/' :
	  case '+' :
	  case '-' :
	  case '(' :
	  case ')' :
	  case '=' : return curr_tok = Token_value(ch);
	  
	  case '0' :	case '1' :	case '2' :	case '3' : 	case '4' :
	  case '5' :	case '6' :	case '7' :	case '8' :	case '9' :
	  case '.' :
	        ist.putback(ch);
	        ist >> number_value;
	        return curr_tok = NUMBER;
	  default:				// NAME, NAME =, or error
	        if (isalpha(ch))
	        {
		    string_value = ch;
		    while (ist.get(ch) && isalnum(ch)) string_value.push_back(ch);
		    ist.putback(ch);
		    return curr_tok = NAME;
	        }
	        error("Bad Token");
	        return curr_tok = PRINT;
      }
}

well Ive used my debugger and my problem seemsto be here:

Code:

  do {			// skip whitespace except '\n'
	 if(!ist.get(ch)) return curr_tok = END;
      }while (ch != '\n' && isspace(ch));

when I was using cin.get it was going trough the string but now using ist (stringstream) it keeps pointing at the first char?

any suggestion on either why is that so or a way to keep track where it should be pointing at and to go to next char...