anchor.diff:  %% TODO: write docstring
   -type result(Value, Error) :: {ok, Value} | {error, Error}.
   
  -%% Macros.
  --define(L(Obj), io:format("LOG ~s ~w ~p\n", [?FILE, ?LINE, Obj])).
  --define(S(Obj), io:format("LOG ~s ~w ~s\n", [?FILE, ?LINE, Obj])).
  +%%% ============================================================= [ Public API ]
   
   -include_lib("kernel/include/file.hrl").
  -
  -%%% Public API.
   
   %% @doc Create a new meta_mod for a module with the given name.
   -spec new(Module :: module()) -> meta_mod().
  
positive.code:     Error    :: term().
  to_src(MetaMod, Filename) ->
    file:write_file(Filename, to_src(MetaMod)).
  
negative.code: %%% ============================================================== [ smerl.erl ]
  %%% @doc Simple Metaprogramming for Erlang
  %%% @author AUTHORS
  %%% @copyright 2006-2007, 2016 AUTHORS
  %%%
  %%% ```
  %%% Permission is hereby granted, free of charge, to any person
  %%% obtaining a copy of this software and associated documentation
  %%% files (the "Software"), to deal in the Software without restriction,
  %%% including without limitation the rights to use, copy, modify, merge,
  %%% publish, distribute, sublicense, and/or sell copies of the Software,
  %%% and to permit persons to whom the Software is furnished to do
  %%% so, subject to the following conditions:
  %%%
  %%% The above copyright notice and this permission notice shall be included
  %%% in all copies or substantial portions of the Software.
  %%%
  %%% THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  %%% EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  %%% MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
  %%% IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
  %%% CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
  %%% TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
  %%% SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  %%% ```
  %%% @end
  %%% ==================================================================== [ EOH ]
  -module(smerl).
  -author("Yariv Sadan (yarivsblog@gmail.com, http://yarivsblog.com").
  
  