code: public Token scanNumericConstant() {
  		int start = pos;
  		while (pos < input.length() && Character.isDigit(input.charAt(pos))) {
  			pos = pos + 1;
  		}
  		return new Token(Token.Kind.IntValue, input.substring(start, pos),
  				start);
  	}
docs: Scan a numeric constant. That is a sequence of digits which gives either
  an integer constant, or a real constant (if it includes a dot) or a byte
  (if it ends in a 'b').
  
  @return