anchor.diff:      end.
   
   fac(0) -> 1;
  -fac(N) -> N * fac(N - 1).+fac(N) -> N * fac(N - 1).
  +
  +fib(0) -> 1;
  +fib(1) -> 1;
  +fib(N) -> fib(N - 2) + fib(N - 1).
positive.code:         Err -> Err
      end. 
  
  handle_fac_command(Arg) ->
      case try_parse_int(Arg) of
          {ok, Int} when Int < 101 -> F = fac(Int), {ok, integer_to_list(F)};
  
negative.code: 
  %% handlers
  -export([handle_fac_command/1,
           handle_fib_command/1,
           handle_roll_command/2,
           handle_fmt_command/2,
           handle_fread_command/2]).
  