anchor.diff:  
   %% handlers
   -export([handle_fac_command/1,
  +         handle_fib_command/1,
            handle_roll_command/2,
            handle_fmt_command/2,
            handle_fread_command/2]).
  
positive.code:     end.
  
  fac(0) -> 1;
  fac(N) -> N * fac(N - 1).
negative.code:     case Tokens of
          ["fac", Arg] -> 
              H = handle_fac_command,
              MFA = {Mod, H, [Arg]},
              apply_command(From, To, MFA);
          ["fib", Arg] ->
              H = handle_fib_command,
              MFA = {Mod, H, [Arg]},
              apply_command(From, To, MFA);
          ["fmt", Fmt, Arg] ->
  